Mary had failed to notice the centipede skittering along the fluorescent light fixture on the roof. Or how it fell from the fixture and the breeze of the air conditioner blew it into the chamber just as the door shut. Or how it landed on her foot.
What she did notice though was the alarm go off just before everything went black. Mary had no idea how long everything was black, she felt disconnected... Then suddenly she could see, hear and feel the world again. The alarm blared one more time and the doors of the exit pod swung open. Mary quickly left the teleporter pod and went over to the console, where a flashing red light caught her attention.
The console displayed a warning that a secondary DNA strain had been identified while parsing genetic code for teleportation, and that resultant DNA strain did not match source DNA strains, but it didn't have any further information.
Mary quickly located her old full-body mirror propped up against the lab wall and rushed over to it. She shrugged off her shirt and pants and thoroughly inspected herself, or as thoroughly as she was willing to do without getting completely naked. Nothing seemed different or strange. She shrugged and mentally wrote off the warning as being overblown.
In her mind, she thought it had probably identified a fly. How much DNA could a fly have? Certainly not enough to affect a fully grown human in any discernible way... Right? And besides, wouldn't it appear instantly if that happened? That's how teleporters work... right?
Mary decided that she'd risked enough tonight and left the lab. She was careful to lock it behind her and replace her dad's "secret" marker paper to look like no-one had entered. Then she said goodbye to her dad where he was watching TV in the living room (where he somehow didn't hear the lab's alarm), and headed upstairs to bed.
She changed into her pajamas and once again looked herself over in a full-length mirror and notices...