Alien signals

Sarah Jane Smith pulled her car up outside Park Vale Comprehensive School, with her son Luke in the passenger seat. She reached into the glove box and pulled out a silvery metallic device with a blue screen. In red lettering the words "Alien Signal Detected" appeared, and beneath it a directional arrow.

"You've got a free period this morning, correct?" Sarah Jane asked.

"Sure, why?" Luke replied.

"Good, you can come with me then." Sarah Jane exited the car, and Luke followed.

"What are we doing?"

"The scanner has detected an alien signal. I suspect it's coming from inside the school. It could be dangerous, and I need your help to track it down and deal with it if necessary."

"Okay, I'll come with you."

Sarah Jane and Luke entered the school, Sarah Jane with her eyes glued to the scanner screen. They followed the directional arrow through corridors, ignoring the students who passed by them curiously. They turned a corner, and Sarah Jane came to a dead stop.

The scanner screen had lit up, showing an image of Sarah Jane and Luke. There was an arrow pointing to their clothes, and the words "Interference Detected."

"What is it mum?" Luke asked.

"It's our clothes. They're interfering with the scanner. We need to take them off." Sarah Jane said.

"What!?"