Matt was sort of getting a kick out of the everyone being invisible thing. They were amused over their floating clothes and he supposed the image was funny. But the thing was, nothing had changed for Matt. He still could sense everyone exactly as he had before. Their body temperature, their heartbeats and pulses, their scent, and of course just basic sounds.
Which is why he knew Kate was in his hallway. He knew the scent of her shampoo as well as he knew his own by now. Her footsteps fell a certain way, even when she was being sneaky - and he would know, as they'd done the whole sneaking around the city together thing.
He had no idea what she was trying to pull here, but he wasn't mad about it. Fine, he'd play along. Getting to his feet, he went to the door and opened it. "Hello?" He called out, trying not to sound as amused as he was. "Anyone out here?"