A shout of terror comes from the room. It's loud but short. The yelp of someone waking up from a nightmare and realizing shortly after that it was just that, a fleeting dream.

It's probably pretty similar to the cries of mage children who encounter their first demons in the Fade. Felix had never really been strong enough with his magic to remember anything more than vague images of the Fade. He had some nightmares when he first got sickened, when the memories of his mother dying had been fresh and too easy to conjure, but he had woken from those dreams silently, sweating and scared but quiet.

This dream, forced onto him by the taint in his blood and Corypheus's False Calling, had been enough to force a scream from him. That's all the sound is though, him waking from a dream fueled by the song in his head telling him he's gone wrong. He bolts upright and sees the faces in the room and realizes he's still alive. There's a noise in his head he can't ignore, but otherwise he's okay.

However, it might be as easy to tell that's all it is when you're on the other side of the bedroom door.