When Ghosts have fulfilled what keeps them on earth, a Crossover Door or "Door to Death" immediately appears in their immediate vicinity. In appearance, the door is entirely ordinary, but leads to the next stage of their existence (or possibly their extinction). This is their "death." This feat was repeated in Becoming Human, when Adam, Christa and Matt, having discovered that Matt had been murdered by his teacher Mr Rowe, shoved Mr Rowe through Matt's door when he tried to attack Adam and Christa, although Adam speculated that this would result in problems in the future.