Marissa Wiegler is a ruthless, vengeful CIA operative who wants to kill Erik Heller, an ex-CIA operative who has trained his daughter, Hanna, to kill Wiegler. One day, Hanna, who feels she is “ready” for the outside world, allows herself to be captured by Wiegler’s men and taken to her facility in Morocco. Not knowing what Hanna is capable of, or perhaps not ready to speak to Hanna in person, Wiegler has a body double speak to Hanna. Shortly afterwards, Hanna kills the double and several others before escaping the facility. Wiegler then begins a manhunt for Erik (who is in hiding in Berlin), murdering Hanna’s grandmother, Katrin Zadek, and interrogating (and possibly killing) a family who befriended Hanna along the way. She enlists Isaacs, a sadistic ex-agent, and his skinhead bouncers to capture Hanna.
When Hanna overhears Wiegler and Issacs talking to each other and saying that Erik is not Hanna’s real father, Hanna learns from Erik that he is not her biological father, but was a recruiter for the Galinka Project, a top-secret program that recruited pregnant women from abortion clinics so that the CIA could alter their children’s DNA and turn them into super-soldiers. When the program was shut down for unexplained reasons, the women and their genetically-modified children were terminated. Erik then tells Hanna he tried to escape with Hanna and her mother, Johanna Zadek, but were attacked by Wiegler, who shot and killed Johanna while Erik escaped with Hanna.
After that, Erik and Hanna try to escape, but are ambushed by Wiegler and Issacs. After Erik kills Issacs and his henchman, Titch, he is shot and killed by Wiegler while Hanna escapes. After chasing Hanna through the woods, Wiegler confronts her at an abandoned amusement park. Hanna pleads for an end to the fighting, saying she does not want to hurt anyone anymore. Wiegler says she just wants to talk, but Hanna starts to walk away.
Agitated, Wiegler shoots Hanna in the hip, who in turn shoots Wiegler with an arrow she shot from a bungee cord. Hanna then chases Wiegler up a nearby water slide, with Wiegler continually shooting at her. At the top, Wiegler becomes disoriented from the arrow and slides down the water flume, dropping her handgun. Hanna follows her down the flume, picks up the gun and tells Wiegler that she just missed her heart, right before shooting her dead.
Marissa is a tall, thin, pale woman, with bright ginger hair, high cheekbones and cold catlike eyes. Her appearance and dress are neat and immaculate, and she is almost always seen wearing gloves, as if she fears touching anything directly.
Marissa is a callous, vindictive villain with little regard for people who get in her way. She is willing to commit murder to get what she wants, although she does not appear to enjoy doing so.
She also appears to be a bit of an obsessive, tightly wound and emotionally volatile. She is consumed by her desire to “tie up loose ends” from her past by pursuing Hanna and Erik, and she is seen vigorously brushing her teeth until her gums are raw and bleeding when particularly stressed. She also seems to be quite paranoid, even depressive, showing palpable dread and anxiety in her confrontations with Hanna and Erik and her murder of Johanna. She is shown to be tough and domineering with her CIA underlings, but struggles to hold her composure with people who bring out her vulnerability.
Her past dealings with Erik are never explicitly revealed, and it is not known for sure why they hate each other. It is implied that the two had a relationship a long time ago, but Erik betrayed her by saving Johanna and Hanna after Marissa decided to terminate the program, murdering all the mothers and their children. She tells one of her officials that she wants to be the last thing Erik sees, suggesting that the motivations are personal.
Her lack of children is also shown to be a sore spot for her. It’s heavily suggested that she views herself as a sort of mother to Hanna, being her “creator”. In her flashback scene, it's shown that she is haunted by Johanna’s last words - “she will never be yours”. Thus, she struggles over her feelings of ownership - and, perhaps, love - for Hanna while also knowing that she had never belonged to her in the first place.