When a new playground game is introduced, the school's social hierarchy is turned upside-down and Gene disapproves. Meanwhile, Linda fills in for the local library storyteller and pulls out all the stops to perfect her storyteller persona.

As the nurses and midwives of Nonnatus House prepare to celebrate Sister Monica Joan's birthday, they face an influx of new patients when a nearby maternity home suddenly closes, leaving many expectant mothers in urgent need of support. Lucille treats a woman whose father has a long-hidden secret he feels he cannot hide any longer, while Tom and Nurse Crane struggle to move forward with their lives.

In a special Dickensian-themed episode, Stewie and Brian are detectives who embark on solving a string of mysterious murders set in Victorian-era London.

Carrie puts a plan in motion. Saul visits a source. Keane makes a desperate plea.

Elizabeth seeks creative solutions when the president of Sri Lanka's psychic convinces him to not move forward with a trade agreement with the U.S. Also, Alison grapples with guilt for missing the warning signs after her college roommate attempts suicide, and Henry makes an abrupt career decision.

Callen, Sam, Kensi and Deeks join Hetty's team from the Vietnam War, Sterling Bridges, A.J. Chegwidden and Charles Langston, in a dangerous and off-the-books rescue mission to save Hetty from her captors in Vietnam. Also, Mosley calls in Nell's sister, homeland security specialist Sydney Jones, to assist the team in Los Angeles with processing evidence connected to Hetty's time in Vietnam.

Megan and Kyle struggle to reconnect under the pressure of planning the most anticipated wedding in Hollywood and preparing for a movie project that could define their careers. Terence and DeAnn find themselves at a crossroads in their relationship.

Daryl finds himself in bad company as his group heads to the Hilltop; Maggie makes difficult decisions at the Hilltop; Gabriel's faith becomes tested.

After barely escaping an explosion at Mason Industries, Wyatt and Rufus chase the Mothership back to a French battlefront during World War I to rescue Lucy. Meanwhile, Lucy recruits Marie Curie, the famous French scientist and the first person to win two Nobel Prizes, to help save the life of a wounded American soldier, knowing only that Rittenhouse wants him alive.

There is a Japanese flavour to this week's show, as Matt LeBlanc and Chris Harris buy second-hand sports cars at auction for a big road trip across Honshu, while Rory has one night to discover the weirdest car culture Tokyo has to offer. Out on track, Chris compares the Honda Civic Type R and Lexus LC500.