Sebastian

Sebastian is impressed by Becky's sharp mind when she spells her name backwards during the interview. Recognizing her intelligence as valuable for his decoding bureau, he offers her a job by giving her his personal number. This is both a professional assessment and a way to recruit someone with exceptional mathematical ability.

Earlier, Sebastian dismisses most people as mediocre, so his interest in Becky signals she is genuinely exceptional.

When Becky accidentally reveals their romantic relationship to the office, it creates a security breach and undermines Sebastian's authority as director. General Phillips had already been suspicious of the department, and the personal entanglement gives him valid grounds to question Sebastian's judgment. To protect both Becky and the operation's integrity, Sebastian resigns.

Phillips had been watching the decoding office closely, particularly after the Shahn security concerns, making him eager to find any reason to remove Sebastian.

Sebastian's condition reflects his loyalty to Shahn, who he previously defended against Phillips's accusations of being a security risk. By insisting on her full pension, he ensures she receives proper recognition for her years of service and validates his earlier judgment that she was valuable to the operation. It also shows he's willing to leverage his expertise for fair treatment of his team.

Earlier, Sebastian argues strongly for keeping Shahn despite political pressure, showing his commitment to protecting valuable colleagues.

Carol is no longer with Sebastian and has taken up with Toby, who is secretly a foreign agent. Together, they orchestrate the rooftop trap to eliminate Sebastian, likely because his reactivation threatens whatever intelligence operation they serve. The LSD incapacitates him, making him vulnerable to being pushed to his death.

Carol's earlier struggles and fading pop career hint at her vulnerability to manipulation by someone like Toby.

Toby is Carol's lover and a foreign agent working against British Intelligence. His attempt to push Sebastian off the rooftop is an assassination ordered by his handlers, designed to prevent Sebastian from successfully decoding the Russian spy satellite signals. With Sebastian dead, the British and Americans would lose their best chance at breaking the Soviet code.

Toby's presence at Carol's apartment seems convenient, and his quick invitation to the rooftop raises suspicion.

Becky and Sebastian had a romantic relationship during her time at the decoding bureau. After Sebastian resigned and left, Becky discovered she was pregnant. When Sebastian returns months later to find her, he learns he is the father of her newborn child.

Their romance develops throughout the film, with Becky pursuing Sebastian despite his initial resistance.

The specific sound frequency and pattern of the baby's rattle provides Sebastian with an unexpected clue to the cryptographic method used in the Russian spy satellite transmission. The noise triggers his insight into the signal's structure, allowing him to begin decoding it with Becky's assistance in her living room.

Sebastian's genius lies in recognizing patterns in unexpected places, which the film establishes early through his code-breaking talent.

Sebastian is drawn to Becky's intelligence and fresh perspective, which contrasts with Carol's fading ambitions as a pop singer. Becky actively pursues Sebastian, and her mathematical background resonates with his own passion for code-breaking. The chemistry and intellectual connection eventually outweigh his existing relationship with Carol.

Sebastian's dedication to work makes him resistant to romantic distractions at first, but Becky's determination gradually breaks through.

The security breach involves suspicions that Elsa Shahn's left-wing political connections may have led to leaks of classified information. General Phillips accuses her of being a security risk, and the tension around her potential involvement creates instability in the department. This culminates in the confrontation that leads to Sebastian's resignation.

Early in the film, Phillips questions Shahn's loyalty while Sebastian defends her value to the operation.

Becky is both a former Oxford mathematics student and a model. After colliding with Sebastian at Oxford, she proves her intellectual abilities by spelling her name backwards during a challenging interview. Impressed by her mathematical mind, Sebastian recruits her to his all-female decoding bureau within British Intelligence.

Her collision with Sebastian is no accident, she actively pursues him after the encounter.