Stan was still trying to wrap his head around Nicky's words (Lying! He had to be lying! Meg wouldn't! She wouldn't do that to him!) when McMillan burst into the room and shoved him.
Stumbling back, Stan hit the edge of the bed and tripped over backwards, arms pinwheeling. He kept his wand up reflexively, protecting it. From his spot on the floor he caught a brief glimpse of Nicky, or at least the back and crown of Nicky's head, before he started rolling to his feet so he could defend himself from Mad McMillan.