Cameron Ducane, walks into a church, hands the priest a baby and then dies of gunshot wounds. No one knows to whom the baby belongs.

Castle and Lanie coo over the little boy who Castle begins calling Cosmo. Kate is a little apprehensive. With Thanksgiving looming and no foster homes available, Castle and Beckett take Cosmo home for the night. They bond over spit up, dirty diapers and lack of sleep.

Castle shares that Meredith wasn't around from the beginning and he had to do it all himself. He's relieved to find out that Kate plans to be his partner in this as well. 

Cameron was forced into a lottery rigging scheme by his boss. When he realized his boss was going to kill Miranda, the woman who chose the lottery balls and her husband and baby boy (real name Benny) he tried to stop it but was killed. But before he died he managed to get the baby to safety.

Beckett and the team rescue Miranda's husband before they can kill him. 

Castle and Beckett prepare to share their first Thanksgiving dinner with Martha, Jim Beckett, Alexis and Pi. 

Castle tricks Beckett into thinking that his family dresses in costume for Thanksgiving. When she shows up in a Pocahontas costume she gets him back by forcing him to wear a pilgrim outfit to dinner.