Henry reaches out to his only ally within Langley, Calder. Joan reveals something during her deposition that puts a wedge between herself and Arthur. An old flame reveals she still holds a torch for Auggie.

When Captain Gregson’s home is invaded, Holmes and Watson work to find the masked gunman before he strikes again. Meanwhile, Gregson gives his team some insight into his private life.

It's Halloween and the doctors of Grey Sloan Memorial are hit with a barrage of spooky patients, which affects their own plans and puts one doctor’s well-being in jeopardy. Meanwhile, Derek collaborates with Ben on a new surgical technique and Richard angers Bailey when he asks a second year resident to perform his next surgery.

The Late Show's annual Halloween costume show; from "Ender's Game", actor Harrison Ford; musical guests Holy Ghost! perform.

Joel and Julia try to keep everything together; Adam and Kristina ask the family for help as they focus on the campaign trail.

When England’s armies threaten Scotland’s borders, Mary asks King Henry for help, but he refuses. Tomas, the son of the King of Portugal, proposes marriage to Mary, promising her aid against England if she’ll abandon Francis and turn to Tomas instead. Francis puts Bash in jeopardy when he lets his feelings for Mary cloud his judgment.

The team investigates Democratic Congresswoman Josie Marcus, while Olivia and Mellie have a surprising run-in during the White House Correspondents' Dinner. Meanwhile, Jake and Huck get closer to the truth about Operation Remington, which could lead to devastating results.

The NSA spying scandal reaches the Vatican, and Codecademy's Zach Sims talks computer programming.

From "Ender's Game", actor Sir Ben Kingsley; author Anne Rice.

On campus, Elena is touched by a sad and secretive student named Aaron. Elena and Damon attend the Whitmore Historical Ball dressed as Anne Boleyn and Henry VIII. At the Ball, Elena shares a dance with Dr. Maxfield, who has a disturbing message for her. Caroline's evening at the Ball takes her from happiness to heartbreak. Meanwhile, Nadia reveals her surprising history to Katherine, and Damon tries to make a deal with Silas. Silas' demand that Damon commit an unthinkable act leads to a violent confrontation.

As Peter settles into a promoted position at the FBI, Neal has to pull off a brazen museum heist right underneath the FBI’s nose.