Zoe Slater returns to Walford

Kat is frantic following the disappearance of son Tommy, and just as she starts to fear that he's gone for good, she gets a message from him that he's outside.

- 

But her relief at hearing his voice is followed by the mother of all shocks he's back with her estranged daughter Zoe, who has returned to Walford after a 20-year absence.