Rick Castle is going to face his toughest adversaries ever in episode 4 of "Castle" Season 7. These adversaries are the kids, as Castle goes undercover at an elementary school. He is about to get schooled, according to the preview of Monday night episode, which is titled "Child's Play."

In the episode, Castle and Beckett investigate the murder of an ice cream vendor. It seems that an unknown second-grader is an eye-witness. To find this kid, Castle becomes himself a kid. He is seen saying in one of the sneak peeks that he is 90 per cent kid himself. He claims to have the ability to get into the minds of the kids.

Castle has a "perfect plan." He is confident that he can handle anything that the little kids can throw his way. He soon realises that he may be 90 per cent but he no longer has any idea about today's kids. He sees that he has under-estimated them. In the sneak peek, Castle can be seen becoming the target of second-graders. They welcome him by throwing stuff at him and they also set a trap for him to see his fall.

In the other sneak-peek, Castle and a kid are playing a game on the wet grass. For a moment, Castle thinks that he has got the eye-witness, but soon realises that the kid is describing a shooting scene that he saw on television. When he gets up from the ground, he realises that his pants are went. The kids can be seen making fun of him, "Mr Castle wet his pants" and one of the kids clicks his photo.

The eyes-witness is expected to be a little girl, as one of the promotional photos features a little girl dressed as a little princess fairy. In this photo, Castle is also sporting wings and has a wand in his hand.

According to "Castle" Season 7 official synopsis episode 4, "Child's Play," "When an ice cream vendor is shot, evidence leads Beckett and Castle to believe that an unknown second-grader may have vital information about the case. Castle goes undercover at an elementary school to try and identify the second-grader but nothing goes as planned."

[Youtube/CastleVitalScenes]

[Youtube/CastleVitalScenes]

[Youtube/CastleVitalScenes]