Who knew a presumed zombie attack could bring two people so close together?

On the penultimate episode of season four, Castle and Beckett battled with the undead on a mostly fun, light-hearted installment of this ABC hit. But we hope you enjoyed the laughter and playful banter... because it's about to get far more serious on next Monday's finale.

Titled "Always," and previewed in this Castle photo gallery, the episode will focus on the murder of an Army veteran - and on Beckett finally tracking down the man who shot her.

Will Castle be able to stop her, by once again uttering those three magic words? And will the final scene depicted at the conclusion of this trailer really go where it appears to be headed? Watch now!

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.