Four By Four was the eighth episode (not counting the Christmas Special) of the second series of Doctor Who Rebirth. It takes place on an unknown Church Planet, and deals with some elements involving the destruction of Gallifrey, Timelords, and The Doctor's past. It also features a new enemy in the form of Husks, which are re-animated Time Lord corprses.

This episode also features the true reveal of The Partner to actually be a new incarnation of the Doctor's arch nemesis, The Master.