Nathan Fillion

Serenity star Nathan Fillion guest-stars on the Nov. 8 episode of ABC’s hit series Lost, "I Do," which also marks the decision by Kate (Evangeline Lilly) to hook up with either Jack (Matthew Fox) or Sawyer (Josh Holloway). Fillion will play a character named Kevin in the episode, which is the last new one for a while as the series takes a 13-week hiatus, returning in February.

In "I Do," Jack makes a decision regarding Ben’s (Michael Emerson) offer, Kate feels helpless when it looks like an angry Pickett (Michael Bowen) is going to make good on his threat to kill Sawyer, and Locke (Terry O’Quinn) discovers a hidden message that may guide him through the next steps on his journey to unlocking the secrets of the island.

"I Do" was written by Damon Lindelof and Carlton Cuse and directed by Tucker Gates. It airs at 9 p.m. ET/PT.