"striped worms with legs in mattress"
Where was the mattress, I wonder. Who turned it over or pulled back the sheet? Who reeled back? Did they make a sound or did they more quietly draw in air past their teeth? Was it a maid at a guest house, or a run-down hotel, or a guest? Or was it an industrialist with secrets at some smarter establishment, and those striped worms with legs are the sort that crawl under your skin into your mind, sucking up thoughts and replacing them with a set of irresistible impulses: 'pick up the phone, tap in this number, and tell the woman who answers all that you know'.
It's such a good thing he found them first and was able to google himself an answer and it is this: Get out now. Run for your life.