Tensions rise when Holmes and Watson are forced to partner with Gareth Lestrade, Sherlock’s former Scotland Yard colleague, on a bombing investigation.

The White House deals with a bombshell announcement from Sally Langston. Meanwhile, Olivia finds herself in a challenging new role.

Jeff helps Duncan romance Britta; Britta runs into some old anarchist friends and discovers they’ve moved on; Abed accidentally destroys some of Hickey’s drawings; Chang has a supernatural experience.

Luke competes against the son of Phil’s nemesis (Rob Riggle) in a wrestling match; Cam and Mitch ask Claire to pick up Lily from school without mentioning the recent lice incidence in her class; Gloria chaperones a field trip.

Frankie tries to persuade Mike to attend a dinner honoring his dedicated service at the quarry; Sue forms a plan to build connections between students; Axl hopes to track down a girl who left a message on his phone.

Oliver brings Sara into the Arrow team. Watching Oliver and Diggle spar with Sara and talk old scars, Felicity starts to feel left out. The team is investigating a villain named William Tockman, a.k.a. The Clock King, who is a brilliant thief armed with technology that can open any bank vault in Starling City. After The Clock King infiltrates the computer systems in the lair, Felicity feels pressure to prove her worth. When she gets a lead on Tockman’s whereabouts, she heads out without the team, putting her in peril. Meanwhile, Oliver throws Sara a welcome home party, but Laurel refuses to attend. After Lance makes his case for a family dinner, Laurel acquiesces, but when Oliver shows up with Sara, she loses her temper on both of them.

With their lives in danger in New Vegas, Monroe and Connor face a difficult decision in order to survive. Back in Willoughby, Miles questions whether he can trust Neville and Jason to help take down the Patriots. Meanwhile, Aaron and Priscilla find themselves at odds over the nano code.

When a guilt-ridden young woman confesses to the murder of a struggling actor — knowing details only the killer could know — Beckett and Castle seem to have an open-and-shut case, until they uncover proof that their suspect couldn’t possibly be the killer. When a second person confesses, equally convinced they committed the murder, the team realizes the case is far more mysterious than they thought.

When Barney suffers from the world’s worst hangover the morning of his wedding, the gang tries to figure out the far-fetched ingredients to concoct the Stinson Hangover Fixer Elixir.

While in Bolivia with Riley to protect a presidential candidate from assassination, Gabriel is shocked to learn his best friend is the suspect.