I thought there was one mouse...

But actually there was 40! and counting. "DIY Pest Control" has amazing non-lethal mouse traps that actually work. They catch up to 5 at a time. It is easy and absolutely worth the money. I can't imagine killing 40 mice. I don't think it would have been as effective. Mice aren't too bright but they probably would have caught on. As it is the more mice caught the more effective the trap became. The mice were attracted to the smell of the other mice. Definitely check it out if you have rodents. They have large rat traps (also non-lethal) and a lot of very good info.