It took nearly seven seasons for Castle (Nathan Fillion) and Beckett (Stana Katic) to finally tie the knot on ABC's "Castle," but it only took two episodes in Season 8 for Beckett to dump her new husband. The conclusion of the two-episode, two-week season premiere ended with an unexpected twist. Beckett, obsessed with solving her mother's murder, decided to take some space from Castle and go solo. However,  the stubborn mystery writer has a plan to win back his bride. What will happen in episode 3, "PhDead"?

According to the synopsis for the new episode, Castle will go undercover as a university professor when the body of a fraternity student at a local college turns up brutally murdered. Castle's disguise will help him and Beckett uncover some dark secrets at the school, including why the college wants to keep the circumstances surrounding the murdered student's death a secret. However, the biggest problem for Castle and Beckett in the episode might not be the murderer(s), but each other. 

The promo for the episode reveals that Castle is relishing his professorial acting gig, but the undercover work is unsolicited. Beckett does not want her husband anywhere near the case, insisting that she wants space to concentrate on herself. However, Castle has it all figured out. 

"Working cases together is why she fell in love with me," the writer promises in the teaser, confident that his sleuth skills will woo Beckett all over again.

Watch the promo for "Castle" Season 8, episode 3 below:

Will Castle's plan work? Will he win back Beckett? Fans will have to wait to find out. "Castle" airs Mondays at 10 p.m. EDT on ABC.