Enjoy seeing Castle act like the big kid that he is? Then, this episode will be right up your alley! Castle goes undercover at an elementary school and cuteness ensues.

*****SPOILERS BELOW*****

Everyone is happy Castle is back and settling in after being gone for two months. Maybe too much, though? Alexis serves the family a huge meal and Castle’s favorite ice cream, Potato Chip Mocha, before Beckett and Castle leave for a new case. Beckett thinks Alexis waiting on Castle hand and foot is a little odd.

Speaking of ice cream, the new case involves finding an ice cream truck under a bridge and murder victim, Anton Vetotchkin. The victim’s parents say he was taking graphic design classes and came home from class upset the night prior. Ryan and Esposito speak with his instructor, Natalie Barnes, who says in the previous class, Anton got freaked out during class. He ran out of the room and she saw him getting in a vehicle with a man.

Ryan determines someone was hiding in the ice-cream truck when Anton was shot. He thinks this witness was a kid, because he also found a class permission slip. Castle and Beckett go to the school to investigate, but none of the kids are admitting to being the witness. Beckett says they need someone who the kids won’t be afraid to talk to and can relate to as one of their own. Obviously, Castle being the big kid that he is, Beckett decides he would be the perfect undercover candidate for this operation.

Esposito tells Beckett the car that Anton was seen getting into was traced to a retired cop, Clark Jaffe. Clark Jaffe is dead, as well, shot to death the same night as Anton; ballistics say it was the same shooter. Initially, the only connection the team can find between Anton and Jaffe is that they went into the same shipping store within an hour of each other earlier in the week. Beckett goes to the store, where she finds out Jaffe and Anton were sharing a P.O. box. The clerk tells Beckett they never got any mail, but they came in twice a week, about an hour apart, to check the box and Beckett realizes they were using the box as a drop-off.

Castle has a plan to get information from the kids by having them write a story. Hopefully, the child witness will write about the experience, letting them know who knows something. The plan seems to be a bust though, when his only lead turns out to be a kid who just saw something in a movie. Castle’s undercover work includes the kids thinking he peed his pants, and making him fall with marbles – so things aren’t going so well for him! When things are looking pretty bleak, a cute little girl named Emily starts opening up to Castle. She tells him that bad things happen to her, too, and just as she is about to tell him what happened to her the day before, her mom is there to pick her up.

The following day, we see Castle wearing fairy wings and having a tea party with Emily, trying to get information out of her. Castle tells Emily if she wanted to talk to him about what happened, it would just be “one princess to another.” One word: adorable. Turns out Emily wasn’t the witness. She just wanted to tell Castle about a class bully, but their interactions were still pretty darn cute. Castle gets thrown out of the class after Emily punches said bully using her “inside strength,” based on Castle’s advice.

The clerk says he saw Anton the day prior, and he seemed worked up after the clerk told him a Russian guy called asking about Anton’s box. Anton didn’t have a cell, so Beckett says they need to check the area around the shipping store to see if anyone let him use their phone and who Anton may have called. After leaving the shipping store, Anton called Dmitri Kalenkov, a rumored enforcer for the Bratva. They find Dmitri, who has been dead a couple days. Dmitri was killed by the same person who killed Jaffe and Anton, but before they were killed. Jaffe’s place and Anton’s parents’ place were tossed, so the killer is looking for something.

Anton’s father, Sergei, found an envelope full of blank passports in his room. Ryan says that since Anton was in graphic design school, maybe he was forging passports. Sergei says that Dmitri and Anton grew up together and were childhood friends. Castle says goodbye to all the kids, and as he’s leaving he finds a piece of paper that was slipped into his jacket. It looks like Emily’s bully, the obnoxious kid Jason, was the one who drew the picture. Jason says he wasn’t in the truck, but he knows who was – his sister.

Jason’s sister is Natalie Barnes, Anton’s class instructor. Natalie says they were all trying to do something good. They forged the documents for Russian immigrants who were stuck here working in sweatshops without the proper documentation to get back home. When Anton was making a passport for a client in class the other night, he recognized him as a terrible person from his past. The man who killed the victims was Polkovnik. Polkovnik is wanted for numerous war crimes, and is trying to get the picture back that was going to be used for the passport, because no one knows what he looks like.

Natalie hid the picture in a camera case, which Jason took to school for show and tell. Polkovnik overhears this while hiding under the bed in Natalie’s room. It looks like it’s a race to the school! Polkovnik meets them at the school and fighting ensues. Castle stops him with the same trick the kids used on him, marbles.

Castle realizes Alexis isn’t handling his disappearance well and is being extremely overprotective. Castle has a heart-to-heart with her and they hug it out.

What did you think of the episode? Comment below!

Castle airs Monday nights at 10/9c on ABC. Catch this and previous episodes on the ABC.Go.com.