'Castle': Season 5 premiere video - best night of their lives...or biggest mistake?

Hear that? It's "Castle" fans sucking up the world's oxygen -- ABC has released the first video for Season 5!

In case you need a refresher, Castle (Nathan Fillion) and Beckett (Stana Katic) finally consummated their relationship in Season 4's gratifying (for everyone, apparently) finale.

"Last season they had the best night of their lives," says the promo, before cutting to the couple's morning-after conversation.

"So it wasn't a dream," purrs Castle, as they lounge in his bed.

"You liked it?" asks Beckett softly, with her hair looking much too fabulous for someone who arrived soaked from the rain and spent the night auditioning for a remake of "Body Heat."

Although both seem to agree with the narrator's "best night" observation, he then continued ominously: "...they'll find out if it's the biggest mistake they ever made."

Phhht. As if.

"Castle" returns Monday, Sept. 24 on ABC.