A gunman holds the team hostage on Christmas Eve.

Sheldon irks the gangs with his obession with proper Christmas gift protocol. Lenoard's crushed when Penny dates a colleague of his.

Sarah's continued obsession with the three dots leads her to a blogger with intimate knowledge of the symbol. Meanwhile, Riley and Cameron face off.

Ted tries to keep his irresponsible sister from hooking up with Barney during her trip to New York, and Robin starts hanging out with Marshall at a bar for Minnesotans, not telling them that she's really Canadian.

Nathan and Peter face off, and Nathan makes a move with devastating consequences. Sylar takes desperate measures at Primatech and the fates of several heroes hang in the balance. Ando, Matt, and Daphne continue their quest to save Hiro.

Michael recieves medical attention. Charles Westmoreland helps uncover the real secrets of Scylla. Lincoln and Sucre do everything in their power to retrieve Scylla before it's gone forever.

Charlie finds himself re-examining his wild ways when an old friend dies.

The gladiators of ancient Rome were the ultimate fighting machines. They waged bloody battles to the death for the entertainment of the masses--and to earn their freedom. From the depths of the vicious and magnificent Flavian amphitheater, to the buried brothel where they lived their last days, these are the secret lives of Rome's famed slave warriors.

With global warming, the Arctic has become navigable, and the race to claim it heats up. As a four-nation conference on the issue unfolds in Toronto, a faraway collision under the polar ice turns a group of Canadian sailors into bargaining chips. Kessler and ICS must find a way to broker a deal that saves the sailors without selling out Canada's future in the Arctic - even if that means betraying personal bonds to U.S. Agent Carver, and British operative Charlotte Bates.

When Sam learns that Dick buys Angela the same Christmas gift every year, he offers to help him get something really special for her... but Sam's attempt to deliver the perfect present does not go as well as he planned.

Local tipsters help the CSI's fight to save their neighborhood from a violent street gang's attempt to take over the area.

Whitney prepares to move to New York and Spencer and Heidi make a holiday trip to Mexico.

Edward figures a way to change identities on his own, but it may be risky. Tom meets up with a stranger who is aware of his alter ego, and Edward is sent on a secret mission by Mavis and Alistair on his own without the usual backup.

Rukia regains consciousness, but is told to rest and regain her strength for the battles ahead. Kenpachi's battle with Nnoitra continues, and Orihime heals Nel at Ichigo's request. Despite managing to have his bankai swallow Szyael, Mayuri inadvertently poisons Uryu and Renji, and Szyael seizes the opportunity to resurrect himself by absorbing Nemu's spiritual particles through his Gabriel technique. However, in the process, he ingests a "super-human" drug from inside Nemu that increases his reflexes to the point where his body cannot keep up, immobilizing him. Mayuri then stabs him through the hand before stabbing him in the heart.

Ric's mind is on Michelle and the grandson he never knew he had as he attempts a risky operation on Callie. A meeting with prospective adoptive parents leaves Daisha even more confused about her baby's future, and Maria learns the truth about Sam's relationship with Kieron. Donna sets to work single-handedly saving Christmas when the staff party is cancelled by hospital management.

The harmony of the survivors is disrupted when they are joined by a spiritual leader and his followers. Al attempts to seduce one of the newcomers. Anya worries that she will be forced to reveal her secret.

Danny Wallace tries to find the best robot made in the world that could be a companion.