I could loan you my 7-lb. dachshund. Years ago, she caught a mouse and shook him, to death. I heard skittering, then there she was, standing with a dead mouse in her mouth! UGH!!! That one got in, via a new dryer, we'd just had delivered!
As others have said, check everywhere for openings. If you live in a brick house, stuff all the weep holes with steel wool or a bit of screening (push it into the hole, with a screwdriver, with the jagged edges facing outside). Any outside holes should either be sealed or stuffed with steel wool/metal screening. Mice can enter through very small spots! If you have a breezeway, to a garage, check where there areas join, at the top. Even after you close the entries, you still need to treat the mice that may already be in the walls.
If you can, call an exterminator. He/she can locate the entry points and provide the best way to safely get rid of the mice.