When a well-respected mathematician is found dead, Holmes and Watson set out to solve a murder and the purpose of the highly guarded equation he was trying to decipher. Meanwhile, Watson is conflicted when the son of a former patient approaches her for a loan.

As the Prom approaches, the race for Prom Queen brings out the best and the worst in candidates Tina and Kitty. Meanwhile, Sam tries to make a connection with a new school nurse, an increasingly discouraged Rachel waits for word on her Funny Girl callback, and Santana makes a new friend at work.

Derek and Meredith adjust to life at home with their newborn and Arizona tries to repair her marriage. Elsewhere, Jackson and Owen clash over financial issues.

Stupid Human Tricks; TV anchor Brian Williams; a performance from the film "Muscle Shoals".

Dara O Briain and the team look back over another week's events with guests Milton Jones, Miles Jupp, Josh Widdicombe and Seann Walsh.

Julia discovers that she has a lot in common with a school parent volunteer; Hank visits unexpectedly and shares advice with Sarah; Zeek doesn't want to talk about the future.

Ben, Leslie and Chris meet with Eagleton city councilor Ingrid de Forest to discuss financial matters. Ann brings April to vet school orientation. Ron tries to get off the grid.

Thomas Shelby's war with the Lee family of gypsies escalates, and Campbell puts further pressure on him to deliver the stolen guns. Meanwhile Thomas's brother John plans to marry a former prostitute, but Thomas suspects that she's still on the game.

Series star Joshua Malina narrates the one-hour special and dissects the rumors, lies and affairs that have made "Scandal" one of the most talked about shows on TV. Viewers will be able to catch up on their favorite characters and story lines from Seasons 1 and 2, and the most asked questions --#WhoisQuinn?, #WhoShotFitz? and #WhattheHuck -- will all be explained.

With Olivia's name out there as the President's mistress, both the White House and Pope & Associates face their biggest scandal to date, and a surprise allegiance is formed in order to get things handled. Meanwhile, Olivia's father, Rowan, will stop at nothing to carry out his orders and no one, including Olivia, can stand in his way.

When the entire gang competes in a cutthroat scavenger hunt designed by Raj that tests their science knowledge and street smarts, it brings out the best – and worst – in everyone.

Congressional leaders fail to compromise on the government shutdown, Stephen officiates a wedding, and David Finkel examines post-war trauma in "Thank You for Your Service".

From "The Bridge (US)", actress Diane Kruger; from "The Hangover" trilogy, actor Ken Jeong.

After spending the summer enjoying her passionate relationship with Damon, and making sure that Jeremy is adjusting after his return from the dead, Elena is thrilled to move into the dorm at nearby Whitmore College with her new roommate, Caroline. Still believing that Bonnie has been traveling all summer and will soon join them, Elena and Caroline are surprised when a student named Megan shows up and announces that she will be sharing their dorm room. Katherine makes an unexpected appearance at the Salvatore house and pleads with Damon to help her now that she is human and vulnerable to her enemies. Matt and Rebekah return to Mystic Falls after spending a wild summer in Europe, where they met a mysterious beauty named Nadia. Elena can’t shake the feeling that something is wrong with Stefan, and Silas makes a terrifying appearance at the “End of Summer” party in the town square.