Homer and Bart become kings of the blue-collar sports circuit, but Marge suspects something dishonest at the core of their father-son bond.

When Avengers Tower is attacked during the holiday party, Happy Hogan must prove his hero chops.

Whitney and Cara become closer as Asher's past comes to light.

In the past, doctors in Sweden and Belgium suspect that Dr. Macchiarini is not running animal trials and is instead experimenting on people. Benita realizes Paolo's promises are lies and uncovers dark secrets from his past.

Strange new behaviors have begun to threaten the day-to-day operations of The Distraction - and one agent is determined to find out who's responsible.

Tae-sang decides to reenter the hospital, but discovers that Ryu Sachimoto is nearby. At the hospital, Chae-ok and Jung-won devise a risky rescue plan.

While HARLOW is on tour, Roger attempts to draw Izzy back into his orbit, but the reappearance of her childhood flame provides the escape she desperately needs.

Long ago, on Christmas Eve, a baby was abandoned in the snow. Today, Ruby Sunday meets the Doctor, goblins, stolen babies and, perhaps, the secret of her birth.

Mike's mum visits, but her attempts to lend a hand drive Alison and Mike mad. To make matters worse, Betty soon senses something is awry with Button House, but does she know what?

It's December 1968. The countdown to Christmas is on, as is the launch of Apollo 8's moon mission. Sister Monica Joan is convinced this could be her last yuletide and that she will not live to see man walk on the moon. Meanwhile, as Shelagh and Dr Turner navigate family life, they are unsettled when a parcel arrives from May's mother in Hong Kong. Sister Julienne makes a very generous offer to allow Colette to move into Nonnatus House for the foreseeable future. Nancy is thrilled to be able to spend every day with Colette and be more present in her upbringing.