Baby, Come Back is the first episode of ALF's fourth season. It originally aired on Sept. 18, 1989.
Kate is pressured by her boss to come in to work, and she is forced to leave Eric with ALF. She somehow gets ahold of Lynn and sends her to pick up Eric and take him along to Brian's baseball game. Brian is supposed to tell ALF, but he is in the backyard when Brian shouts the message.
When Willie comes home, ALF explains that Eric is inexplicably missing. The two are relieved when Kate returns and tells them that Lynn has the baby.