Monet Mazur and Nathan Fillion, Castle

Beckett's new love interest on Castle isn't the only obstacle to a Castle-Beckett pairing.

Monet Mazur will return as Gina Cowell, Castle's ex-wife and book editor, in the Season 2 finale, TVGuide.com has learned exclusively.

Castle's Stana Katic: Beckett's ready to tango with new love interest

Cowell, who last appeared in the show's pilot, turns up because Castle (Nathan Fillion) has fallen behind on his latest book. Gina hopes to get Castle back on track — in more ways than one.

The old flame will be rekindled, creating some interesting reactions from Beckett (Stana Katic). However, Gina's reappearance may just open both Beckett's and Castle's eyes.

Check out photos of the Castle cast

Mazur has recently appeared on NCIS: Los Angeles, CSI: Miami and Cold Case.

Castle's season finale airs May 17 at 10/9c on ABC.