kimmy

My cat sneaked outside last night and brought a tiny little field mouse into the house for me, lost interest in it and dropped it. My other cat is trying to get him, but I have noticed that he isn't trying to kill him, he wants to play. He scared him and he is now under the fridge, it might be a female and I don't want it to give birth or chew on wires. I have the kitchen closed off, how do I catch this mouse humanely?