<i>Castle</i>, Brendan Hines Castle, Brendan Hines

What happens when a mystery writer has his muse stolen by his protégé? If the writer is the title character of ABC's Castle, the answer is simple: It gets combative.

Check out photos of  the Castle cast

TVGuide.com has learned exclusively that Lie to Me star

Brendan Hines has been tapped to play Alex Conrad, a first-time mystery writer who owes some of his debut novel's success to a glowing review written by Castle (Nathan Fillion). When Castle invites Alex down to the precinct to play mentor, however, Alex becomes much more interested in what Beckett (Stana Katic) has to say about being a police detective.As Castle and Beckett investigate a swimming star's murder, Castle becomes increasingly agitated by how willingly (and privately) Beckett shares information with the newbie author. But don't think the jealous Castle will go down without a fight.

The episode also guest-stars Make It or Break It's Josie Loren and Justin Bruening, the star of NBC's short-lived Knight Rider reboot. Bruening plays the victim's swimming coach, while Loren plays the victim's former girlfriend. Naturally, they both become suspects.

Watch full episodes and clips of Castle in our Online Video Guide

Besides his work as Eli Loker on Fox's Lie to Me, the 34-year-old Hines has also appeared on The Middleman and Terminator: The Sarah Connor Chronicles.

Castle airs Mondays at 10/9c on ABC. Hines' episode, titled "The Dead Pool," is slated to air sometime in April.