In the middle of a blocked road, a yakuza man named Oda wakes up, finding himself in
just his underwear and in front of Bok Soon, the legendary assassin.
Instead of killing him immediately, Bok Soon explains she learned from her daughter Jae
Yeong that things should be done fairly, which was discussed when they heard the news about
the senator refuting all claims that his son was fraudulently admitted into college.
So in order to be fair, Bok Soon gives Oda a sword so he can defend himself while she'll
fight with a hatchet.
A fierce battle begins between two very skilled warriors, but in the end, it's Oda who kills
Bok Soon.
However Bok Soon is suddenly seen alive as well, because that fight had just been her
analyzing the situation and predicting the result.
Seeing as she can't win hand-to-hand, she decides to cheat and just shoot Oda.
Afterward Bok Soon goes home, where she discovers her daughter has been hiding cigarettes.
This makes Bok Soon remember when her abusive father found her smoking and made her eat
a cigarette.
When Jae Yeong gets home, Bok Soon goes through many scenarios in her mind and seeing they
all end in an argument, she decides not to scold her, since their relationship is already
pretty tense and awkward.
Jae Yeong doesn't know her mother is an assassin and hates how secretive and absent she can
be.
The next day, Oda's death appears on the news.
Min Kyu is glad to see Bok Soon did her job well because he's the CEO of MK Enterprise,
the assassin company Bok Soon works for.
However his sister Min Hee is jealous because she knows Min Kyu adores Book Soon and pays
more attention to her.
Meanwhile Bok Soon gets together with her hitmen friends for a drink.
Everyone is impressed by her sword and her salary, which is quite high because she's
class A and the best in the business.
While they chat, they discuss the three rules Min Kyu has taught all the assassin companies:
never murder minors, only take jobs sanctioned by their companies, and always attempt the
assigned jobs.
Disobeying these rules will get the employee killed.
After the meeting is over, Bok Soon finds a group of thugs checking out her car and
calling her naughty names.
Bok Soon insults them back, but before they can react, fellow assassin Hee Sung cuts in
and beats them all up.
Hee Sung is as good as Bok Soon and should be class A as well, but he couldn't go that
high because he got on the CEO's bad side.
After the fight, Bok Soon and Hee Sung spend the night together, and Bok Soon gives Hee
Sung money for his father's medical treatment, which hurts Hee Sung's pride.
Meanwhile Jae Yeong is meeting with her girlfriend So Ra.
Their relationship is a secret because they know their mothers wouldn't approve of their
preferences.
Unfortunately they have to interrupt all their kissing when a group of classmates almost
walks on them, and Jae Yeong has to turn down Cheol Woo's invitation to hang out, which
makes him rather angry.
Sometime later, Bok Soon goes to the MK offices to see Min Kyu, but Min Hee blocks her way
and drags her away for a special activity.
In a shady bathroom, Yeong Ji attacks a man, triggering a fierce fight that throws them
against the wall, revealing this is just an exercise in the assassin academy.
Min Hee puts Bok Soon on the spot and asks her to train with Yeong Ji, who is her biggest
fan.
Yeong Ji arms herself with a wooden knife and Bok Soon with a marker, and the fight
starts with an obvious advantage for Bok Soon.
Yeong Ji manages to pull a trick to throw his weapon from one hand to the other, which
would've given Bok Soon a cute if the knife had been real.
However Bok Soon quickly retaliates and uses her marker to write on Yeong Ji's neck, which
would've equaled death.
Afterward Bok Soon meets with Min Kyu, who makes her choose between two envelopes for
the next mission.
Book Soon looks at her choice and discovers she must kill a boy, but Min Kyu quickly corrects
her and explains he's of age.
Bok Soon also takes the chance to remind Min Kyu her contract is ending soon and she'll
be retiring.
Their meeting is interrupted when Bok Soon gets a call from the school telling that Jae
Young stabbed Cheol Woo.
She rushes to the school and learns that her daughter is at risk of being expelled because
she never gave a reason for the attack.
For now she gets a week of suspension, and then the committee will make a proper decision
later.
Afterward Bok Soon talks to Jae Young and demands an explanation, but Jae Young just
says she wanted to kill Cheol Woon.
Later while Hee Sung is on a job cleaning the bodies he left, Bok Soon offers her company
and rants about how distant she feels from her daughter.
She's also worried that Jae Yeong is becoming too much like her.
Meanwhile the leaders of each assassin company under MK are having a meeting.
They've discovered there's a murder victim that happened outside company's orders and
the culprit could be one of their employees.
Min Kyu assures everyone that if that's true, he won't hesitate to kill the culprit for
breaking the rules.
They don't know this is all a plan by Min Hee, who wants to get rid of Bok Soon to have
Min Kyu for herself.
Sometime later, Bok Soon keeps on trying to talk to Jae Young, but the girl ignores her.
At that moment she gets a call from Min Kyu, who is getting ready to go on a trip, and
he informs her that Yeong Ji will be her partner for the mission.
Later in the evening, the two assassins break into the victim's apartment and knock him
out, then they begin preparing the details to make it look like he did it himself.
But when she's about to kill him, Bok Soon realizes the face looks familiar and checks
the goodbye later: it turns out this is the senator's son, who the father is getting killed
to get rid of the scandal.
Her thoughts are suddenly interrupted by a call that goes directly to voicemail, and
she listens to the message to discover it's Jae Yeong apologizing for everything.
Inspired by this, Bok Soon refuses to kill a young man just because his fathe's ashamed,
so she calls Min Kyu to tell him she's made a mistake and failed the mission.
Min Kyu has already arrived at a Russian bar and he puts on his earbuds to talk to Bok
Soon while he carries on his mission.
A fierce battle ensues in the bar but Min Kyu has no issues fighting and killing every
man that approaches him with accurate shots or hand-to-hand combat.
As he fights, he demands to know the truth, but Bok Soon sticks to her story and even
makes Yeong Ji say she also made a mistake to make it more believable.
Min Kyu points out Bok Soon broke the rules, so to buy his silence, Bok Soon says she'll
accept to extend her contract with MK instead of retiring.
Her only condition is that nobody can finish the mission she failed, and Min Kyu accepts.
When Bok Soon gets home, Jae Yeong is already sleeping.
However when she leaves the room, it's revealed that Jae Yeong was just pretending to be asleep,
and she's been needing comfort because So Ra won't answer her messages.
After finishing his own task, Min Kyu calls Min Hee and tells her to close the senator's
case, ignoring the fact this could damage the company's reputation.
Min Kyu has a clear preference for Bok Soon and it makes Min Hee hate her more.
Ready for revenge, she goes looking for Hee Sung to ask him to finish Bok Soon's failed
mission, which he immediately accepts because it would put him in the A leagues and give
him the money for his father's treatment.
On the plane, Min Kyu can't help thinking about the day he met Bok Soon many years ago.
When Min Kyu broke into a house to kill a man, the guy's daughter came home earlier
than expected.
This was Bok Soon, who wasn't bothered by the fact someone was trying to kill her abusive
dad, in fact she kicks the chair to finish the job.
Min Kyu had been impressed by the girl's lack of fear and quick thinking, so he took her
under his wing to train her as an assassin.
Sometime later, Bok Soon finally gets to have a proper talk with her daughter, who shares
what truly happened.
Cheol Woo took a picture of her and So Ra kissing, then he threatened with making them
public unless Jae Young dated him for one month.
To make matters worse, So Ra asked Jae Young to do what he said for the sake of her reputation.
Hurt by her girlfriend's lack of empathy, Jae Young responded by stabbing Cheol Woo
with a pair of scissors.
Bok Soon is quite upset to hear her daughter likes girls and asks her if she's just confused,
which hurts Jae Young deeply and makes her remind her mother she keeps secrets too.
Their conversation is interrupted by a visit from Yeong Ji.
Bok Soon thinks this is an attack, but she immediately calms down when Yeon Ji explains
she's been fired because she's being blamed for the failure to cover for Bok Soon.
Feeling guilty and pitiful, Bok Soon takes Yeong Ji to the bar to have dinner together,
and Jae Yeong has to watch how her mother chooses work over her again.
At the bar, Bok Soon's assassin pals arrive with Hee Sung as they congratulate him for
becoming A rank, which immediately tells Bok Soon that something's wrong.
Meanwhile Min Kyu violently confronts Min Hee for finishing the senator's job, but Min
Hee responds by trying to kiss him.
Min Kyu turns her down and sticks to defending Bok Soon.
At the bar, Bok Soon sees the news of the boy's death and immediately guesses what happened.
Her scolding of Hee Sung is suddenly interrupted by a call from Min Hee, who asks to be put
on speaker.
Then she offers the mission of killing Bok Soon, whoever manages it will jump straight
to rank B. Another savage fight begins that even the bar owner joins, and Bok Soon is
shocked to see Yeong Ji is actually on her side helping her kill each of the guys.
One by one they kill every single assassin with whatever tool they can find around, and
lastly only Hee Sung is left.
When Bok Soon comes to kill him, Hee Sung asks her to take care of his dad before he
dies.
Afterward Bok Soon calls the cleaning crew and wonders why Yeong Ji helped her, so Yeong
Ji explains she just wants to survive and Bok Soon had more chances of winning.
Then Bok Soon gets a call from Jae Young, who wonders when her mother will come home
because she needs her.
However Min Kyu suddenly shows up and violently pushes Bok Soon against the wall, furious
because she's broken a bunch of rules and this will get him in trouble with the other
leaders.
Bok Soon doesn't want her daughter to hear this, so Min Kyu quickly destroys the phone.
Then Yeong Ji cuts in and explains that it was Min Hee who sent the orders.
Min Kyu asks Bok Soon to come to the office the next day to renew her contract because
that's the only way he can protect her, but Bok Soon refuses, knowing that this disrespect
means they'll have to fight.
However when she calculates the outcome, she can see she loses, so she has no choice but
to accept to renew the contract.
After Bok Soon leaves, Min Kyu asks Yeong Ji not to tell anyone about this.
At home, Bok Soon is scolded by her daughter, who had been worried because she didn't answer
her phone.
Jae Yeong explains So Ra has broken up with her and is now denying she's into girls like
that.
Bok Soon apologizes for her reaction earlier and promises Jae Yeong she doesn't have to
hide who she is.
Then she has a breakdown, and Jae Yeong realizes her mother has had an awful day at work too.
They bond over their difficult lives while Bok Soon continues to keep details vague,
but Jae Yeong suddenly confesses she once found a gun and a fake passport in her mother's
bag.
This makes Jae Yeong think her mother is CIA, and since Bok soon finally feels close to
her daughter, she doesn't deny it.
The next day the company bosses hold a meeting to discuss the killing of their men, suspecting
that Min Kyu is involved in this.
Min Kyu explains Bok Soon had been defending herself and offers monetary compensation,
but some of the bosses don't believe him and ask him to finish things for himself as the
rules say, even handing him the blade to do so.
Instead, Min Kyu kills one of the bosses on top of the table and reminds everyone that
he is the rule, so he adds a new one to the list: not drawing weapons during their meetings.
Meanwhile Bok Soon goes to the office to sign the contract, only to find Min Hee, who confesses
Yeong Ji was killed by Min Kyu after she left the other night.
Furious, Bok Soon kills Min Hee with a pen and leaves it for Min Kyu as a message that
she wants to duel him.
In the evening, Bok Soon makes sure to have a very cozy dinner with Jae Yong, even letting
her skip the vegetables.
She wants her to have a last good memory in case she doesn't come back.
Moments later, Bok Soon arrives at the office, and Min Kyu begins shooting at her as soon
as the elevator doors open.
However Bok Soon doesn't move, knowing he isn't being serious yet.
Then Min Kyu asks her to have a drink with him, saying he's already predicted the battle
and that she loses.
Bok Soon begins going through dozens of predictions in her head, using all kinds of techniques
to try to kill Min Kyu each time, but no matter what she tries, she always ends up losing.
However hearing him talk about the old days makes her realize he does have a weakness,
and that's Bok Soon herself.
It turns out Min Kyu had been in love with her all this time, and when Bok Soon finally
says it aloud, it's enough to distract Min Kyu and kill him with a samurai sword.
Before dying, Min Kyu confesses he sent a tablet to Jae Young so she could watch everything
through the security cameras.
Panicking and upset, Bok Soon rushes back to her home, afraid her daughter will hate
her now.
However Jae Young is asleep in her bed, so maybe Min Kyu was lying.
At that moment Jae Young wakes up and praises Bok Soon for always working so hard for the
family, which makes her feel guilty and leaves her wondering if Jae Young truly doesn't know.
Sometime later, it's revealed that the senator that got his son killed died in his car due
to carbon monoxide poisoning, implying Bok Soon did it.
Jae Yeong has officially been expelled, but she goes to the school to say a final goodbye
to her friends.
She shakes hands with So Ra and leans in to whisper in her ear that she debated whether
to kiss her in front of everyone or to just kill her.
Afterward she makes eye contact with Cheol Woo as she touches her neck, reminding him
what she's capable of.