Sam follows Jack Turner as he leaves to take a late-night meeting at a local university. Along with Stephen's friend Lewis, Jack pays a visit to Vincent Cage, Lewis's old university professor. When Cage refuses to go along with what Lewis and Jack ask of him, Jack smashes his head in with a ceramic bust, killing him. They spot Sam in the window and chase after her, but Sam escapes, unsure if she's been identified.
The next day, Sam accompanies the Turners to the gravesite of Stephen's wife, where "Alex" is formally introduced to Lewis. Lewis asks Stephen for permission to ask her out, and they make plans to meet that night.
Crane confirms to Keel that he knows Aidan is the mole, but he hasn't been able to prove it yet. Keel invites Natalie Thorpe into his office and offers to pay her to reveal MI6's mole, but she refuses.
Aidan discovers the hidden room in Sam's flat where she's been posting clues on the wall, trying to piece together who wants her dead. He sees the word "Hourglass" and asks a researcher at Byzantium, Simran, to look into it for him off the record.
Fowkes, having worked his way into Dave Ryder's good graces, is summoned to his new friend's bar. There, he meets Tyrone, who gives him a chilly reception. Tyrone has him place a bag inside the trunk of a local pimp's car. Fowkes peeks inside and sees the bust that was used to kill Professor Cage.
At Byzantium, Zoe debriefs the team about Lewis and Turner's relationship. Lewis, under Cage's tutelage, has developed an algorithm called "Kismet," which has made a tremendous amount of money for Turner's company by profiting off of unexpected disasters.
Simran tells Aidan she's discovered that the Russians had kept a file on MI6 officer George Ballard, who himself had kept a file on Hourglass. The Russians ceased to keep tabs on him when he transferred to London, but Thorpe, Aidan's MI6 handler, reports directly to him.
At Lewis's apartment, he warns Sam that he knows it was her outside Cage's office. She feigns ignorance and when he buys into it, she touches his arm flirtatiously. As he embraces her, she pricks him with a sedative and sneaks out with his key card. She meets Aidan outside, and they break into Lewis's office, where they discover emails detailing the Kismet program. They realize that the spikes in Turner's company's earnings correspond with tragic "accidents," which Turner has actually been causing. Their presence attracts the attention of the building's security guards, and the two barely escape, but when Lewis comes to, Sam's lying next to him.
Tyrone takes Fowkes to a subway station and has him stand guard outside. Inside, Ryder's henchman saws through a pipe and causes a gas leak. The next morning, Aidan realizes that Turner plans to blow up the Goncourt and Co. building to raise the $30 million he needs for the Khyber Dam bid. Just as he prepares to run away, the building explodes and Aidan is caught in the blast.
At the exact same time, Sam is pinned down by the Blank-Faced Man, who places a needle through her eye.