Brief summary. Brief. I can do this.
Basically, the primary murder suspect in Beckett and Castle's case says he's from the future... Beckett thinks it's silly, Castle thinks it's amazingly interesting. Things get more and more complicated when another supposed time traveler enters the picture. Apparently, some big event from this time period will cause a ripple effect into the future and kill millions of people. Blah blah blah, the usual cliched time travel story.
I liked Ryan and Esposito in this one, because they thought the whole thing was as ridiculous as Beckett did, and they didn't even think the crazy guy's story was any good. It was also funny to see Castle get sucked in to the guy's wacky story, especially since the supposed time traveler seemed extremely... sane. Yeah, he seemed like a pretty normal guy, which I really liked.
In the end, they discover that the bad time traveler guy wants to kill this one grad student who (according to people "from the future") is going to play a big part in saving the world in a giant energy war. Beckett and the team stop the guy from getting murdered, which supposedly restores balance to the future world.
So here's the biggest problem with the episode - apparently, the reason these two guys both have the same crazy story about the future is because they were both in a mental health facility together several years before. What a lame ass solution to a really interesting problem. I found myself wishing that this was the type of show that would allow for fantastic possibilities like time travel, because I found the whole story very intriguing. Despite the cliched nature, I was drawn in by the characters and by the mystery, which involved an energy conservation extremist group, a bunch of scientists, and some nifty little hints about Castle and Beckett's own future - apparently they have three kids, and Beckett becomes a senator!
To have all of that lead up to such a lame conclusion...they were both mentally unsound, it was like saying - just kidding this is all nonsense! That felt really weak. Then we get this tantalizing little moment where Beckett spills coffee over a letter and then sees a picture of the same letter that they'd already gotten from a person in the case, and the coffee stain is on the copy of the letter. What does that mean? Does that mean time travel is a real thing? Are they ever going to go anywhere with that? Probably not! Which is definitely super annoying!
The subplot involved Alexis deciding to move into an apartment with Pi. Castle doesn't like it (obviously) and tries to convince Alexis not to. But she says she's responsible enough to make this decision, and she moves in with Pi. It was all a lesson in letting Alexis grow up, which would be fine if we hadn't already seen the same exact lesson on this show tons of times before.
Some people seem to be really excited about this episode, and all of the time travel stuff. But for me, I'm just annoyed - obviously this time travel thing isn't going to come back. So why include it? Why have another episode with the same formula as we've seen before - Castle buys in to a crazy theory, Beckett doesn't let herself believe it. And why have we reverted back into our old formula of the past five years, completely erasing the development of Beckett's job in DC? That's really bothering me.
While not a super strong episode, the plot itself kept me really entertained up until the end.