Google, or search, Box traps. The simplest would be to use a half a pencil with a long string tied to it. Put down some bait and set the box on top of it bottom up. Lift one side of the box and prop it with the broken pencil. The gap has to be big enough for the mouse to get in and small enough that the mouse wont get out before the box falls. Go accross the room and hold the other end of the string, then wait. When the mouse goes under to get the bait just pull the string catching the mouse under the box. Carfully slide another piece of cardboard underneath and slowly flip the whole thing, then retrieve your mouse.