I was racking my brain trying to remember where I'd seen Brendan Hines, the actor who played the young novelist. Eventually I gave up and checked IMDb, and couldn't believe I'd forgotten he was Tyler on The Middleman, one of my favorite shows of recent years. He was also Andy Goode on Terminator: The Sarah Connor Chronicles.
I clocked him the instant he showed up. God I miss The Middleman.
On a slightly more upbeat note, It was great to finally end an episode with Beckett and Castle having a moment that isn't rudely interrupted. That schtick was getting old.