You'd think Mona's birthday party would be boring, but you'd be wrong. She's got a whole "Camp Mona" theme set up, and she calls it glamping, so basically the girls get goodie bags and massages in the woods. Most notably this leads to a scavenger hunt set up by "A", which all the girls willingly participate in. Hanna can't get glamped up while waiting for clues though, since Mona disowned her as a friend after "A" sent a text message saying that Hanna had lipo to get skinny. Oh, and because Hanna's poor now, but that Melrose Mom does her best to hide that fact.
The FBI have taken over the case and I'm sad about this if it means no more nearly-naked Det. Wilden. They've got the video that "A" sent that has Alison flirting in front of a camera operated by her mystery man the day she went missing. The sweater she's wearing belongs to Toby, so that makes him the prime suspect, which is convenient for when he returns to town to chat up Emily in the woods. Not creepy at all, but after he confesses that he did give Ali his sweater, but saw her go off with some older guy, he hides out behind the church and Emily turns him in.
Also returning to Emily's life: her dad. It's a nice-ish reunion, even if Nia does kick Maya out… and that's before she finds the pictures of Emily and Maya kissing.
Ian has also returned -- he's the other guy Melissa was dating who Spencer made out with. Alison caught the two of them making out and said it was skanky, essentially, but then we find out that Ali was the skanky one, as she was the one hooking up with him in the video. Giving Alison just one more reason to hate Spencer.
Also, Fitz wrote a sexy poem about Aria, then saw her kissing Noel and got weird again and then they made out in his car for a long time. Melissa is slightly less bitchy to Spencer for half a minute. Aria and Emily end up with ridiculous hair from Mona's party. Melrose Mom stole some old lady's cash from her safety deposit box. And Hanna figures out who "A" is… just in time to get hit by a car and rendered unconscious.