Sam (Karen Gillan) was only 12 years old when her mother Scarlett (Lena Headey) was an elite assassin and she was separated from her mother. Sam was raised by The Firm, the ruthless crime syndicate her mother worked for. Now, 15 years later, Sam has followed in her mother's footsteps and grown into a fierce female assassin. She uses her "talent" to clean up The Firm's most dangerous messes, both capable and loyal. But when a high-stakes job goes wrong, Sam must choose to continue her loyalty to The Firm or protect the life of an innocent 8-year-old girl, Emily (Chloe Coleman). Sam has become the target of the hunt, and now she has only one chance to survive: reunite with her mother and other female assassins "The Librarians" (Michelle Yeoh, Angela Bassett and Carla Gugino). These three generations of women must now learn to trust each other, stand up to The Firm and its army of minions, and rise up against those who can take everything from them.