So we moved into this big old handy mans special of a house?

I'm dealing with the same thing right now. Whats worked for me is putting steel wool in any crevice a mouse can enter, but leave on open. Check your whole house well and close them all up. The one thats left open place lots of poison and traps. I've caught at least 12 now and havent seen droppings in three days. Check regularly and replenish poison. Good Luck!