A Nervous Tick.

You tell Ann to call the police so you can give them a lead and catch the killer.

But just as Ann reaches for the phone, she finds an unusually large American dog tick on her arm and immediately falls into paralysis... unable to move— again.
Chad and the dog.

10 hours have passed— and still, you’re trying to flick the large tick, the size of two thumbs, off Ann’s arm who by then is burning with high fever and convulsing in a seizure.

Still, the dog doesn't move an inch, and unfortunately, neither can you even if Ann struggles with her last breaths.