Suddenly, footsteps approach Avi from behind. And not just footsteps — feet. And the legs and person who they belong to. Avi turns around and finds herself confronted with the angry scientist she thought she'd got away from.

"Stranger! Stop immediately! You are not safe here!" the scientist yells.
"What? There's absolutely nothing threatening in here," Avi says, confused, but choosing not to mention the scientist's demeanor as the sole exception so far.
"It's Cleaning Day!"

"There's a cloud of violent micromachines coming through in the next few minutes to clean the tunnel of all biological life! Like it does every week!"

Avi hated strict schedules.