Afraid they will never get pregnant, Lily and Marshall decide to see a specialist. Robin begins her new job.

Lily and Marshall receive shocking news that has a profound impact on the gang. Ted begins his duties as best man for an old friend’s wedding.

Abed wakes up in stop-motion animation making him believe that the group must re-discover the true meaning of Christmas. With the help of Professor Duncan, the group explores Abed’s winter wonderland and soon discovers the truth behind Abed’s madness.

When the Fringe Team investigates a case where a victim had his heart extracted, it’s just the beginning of a series of mysterious and reanimating events tied together. Meanwhile, Peter comes to terms with the reality of his relationship with Olivia.

At Luke and Manny’s first school dance, Jay and Phil take them to the mall which turns disastrous, Claire’s is jealous when Gloria joins the school dance committee. Cameron and Mitchell learn about Lily biting other kids at the playground.

As the Warehouse team prepares to celebrate the holidays in snowy South Dakota, Pete and Myka are called upon to hunt down a malevolent Santa Claus. Meanwhile, in time for Hanukkah, Artie and his estranged father, Isadore Weisfelt reunite after 30 years.

When Ted’s new friendship with Zoey tests the theory that single men and married women can’t be friends, he invites her husband, « The Captain, » to hang out with them. Meanwhile, Marshall and Robin decide to spend alone time together, and Barney and Lily possibly have a fight.

It is Troy’s 21st birthday, so the group decides to hit the bars. While Britta and Jeff are drinking too many cocktails, Shirley is taking down incriminating pictures of herself, Annie is embracing her fake identity and Abed gets into a deep conversation with another Sci-Fi lover.

Peter struggles to cope with recent events; Olivia searches for an ally; a device that communicates between universes is discovered…

The crew’s new-found control over Destiny’s flight path introduces new risks when they find themselves in the middle of a war between two races.