It wasn't a rat, it was a mouse. And it was sitting on the carpet in Sam's bedroom bold as brass, then it ran behind the toy boxes when it saw me. That's great for two reasons. First, I'd much sooner have mice in the house than rats. And second, we now know where to put the trap - behind the toy boxes in Sam's room.
Sorry Andrew, I take your humane arguments on board but it's in my actual house, it's a fire hazard, a vector for disease, and I don't feel any qualms about getting rid of it in the most effective and efficient way I know how. In fact it was my husband Ed, a strict vegetarian, who bought the traps and set them. Maybe now I can persuade him we should get a cat.