Greetings,
Often people have mice so they set one little trap where they think the mouse might be. Traps are 4/$1 at my local dollar store. That means for $5 you could purchase 20 traps. If you don't know where the mouse is, and you hate them as much as I do, consider placing a trap everywhere anywhere near where you heard a mouse. This is what I do for my tenants and they love the results. Once the infestation is gone the zillion traps can be removed.
Hope this helps, William
PS: If you ever find a hole in wall shove it full of poison and close it off. If you know what wall they are in and for some reason you don't like traps or poison on the ground (pets and tots maybe?) you can try the following:
a) remove a receptical or light switch (you don't have to disconnect the wires-- the receptical can be unscrewed and pulled away with the wire still attached) b) remove a "knock-out" from the box the outlet is in if the box is metal c) put poison down through the hole d) put a knockout plug back in the hole e) screw the receptical back on