Castle (2009): Season 6, Episode 10

6 - 10: The Good, the Bad and the Baby

Bleeding man stumbles into a church, but just before dying, he hands a mysterious bundle to the priest. When the bundle turns out to be a smiling baby boy, Castle and Beckett find themselves accidental nannies to the newborn. But when they determine the baby and the victim were not related, they discover that finding his rightful parents may be just as hard as solving the murder.