Will goes willingly where House pulls, though he listens to the squeal from behind them. Again, there is a part of him that feels genuine sympathy for Sylar, an understanding of what the man/creature wants. But he's simply not prepared to let him have it, particularly at the risk of House's safety.

It takes both his hands to figure out how to work the knob, the pain from all that electricity is starting to overwhelm the adrenaline in his system, but he gets the door open. One of his hands reaches back, trying to scrabble at House to ensure the doctor comes in with him, relaxing only once he hears the door slam shut.

Falling on the ground in an undignified heap, Will's head hung and he whispered.

"Sorry."

Whether the apology was to House, for not being able to help hold the door, or to Sylar on the other side, was anyone's guess. Hell, it probably was to them both.