Something is scratching in my floor with long nails and its not a mouse!

Every night for the past 5 days i hear a walking/scratching noise in my floor a couple times a night.It drives my cats crazy and me trying to find it and see what it is,the problem is it does not sound like the small pitter patter of mouse feet but like a larger heavier animal/thing.Ive seen a flying squirrel around here since then also and have wondered if it could be it.We have a brick house with no holes anywhere but a dryer vent and central vacuum vent with flaps covering them.Do you think it could of gotten in through the dryer vent by flipping the flaps that let the air out and chewed a hole in the plastic hose and set up its winter house in OUR house?Im beside myself here and scared to wake up to somethin staring me in the face in the middle of the night,haha.What would you do?Put a trap?Put a grill with small lines over the dryer vent,etc??HELP!!