Best friends Debbie and Judith's world turns upside down when Debbie learns Judith isn't a forensic accountant—she's an international assassin. When a figure from Judith's past emerges and a hit goes wrong, they're forced to run.

After the Gala, Judith tries to find who set her up. Debbie searches for answers about her husband and makes a shocking discovery. The Director gives Judith one last chance, and Sam finds Billy Donovan's hideout

Debbie and Judith's road trip takes a turn when they're forced onto a luxury train, only to discover they've been followed. Sam's one night stand isn't what she seems. Queenie helps Sam find a body. Debbie makes a shocking discovery.

Judith and Debbie reach Spain, reeling from the truth about David. The Director gives Judith an impossible choice. Detective Boucher investigates a body on the train. Debbie and Judith hunt for Billy Donovan together.

An unlikely trio heads to Monte Carlo for David's missing money. Judith uses an old cover, Debbie devises a risky plan, and neither trusts Billy. Sam disappoints Queenie. Mrs. Williams gets a visit from a former colleague.

All roads lead to Geneva as everyone closes in on the money. Judith finds unexpected guests, Interpol and the Albanians move in, and romance blossoms. The plan goes sideways, leaving Judith and Debbie in mortal danger.

Back in London, Judith and Debbie's friendship seems broken. Queenie learns a shocking truth, Sam faces consequences, and the Director takes Judith back. As Ana's plan unfolds, Debbie and Judith race toward a spectacular finale.