Happy Trails (through the bathroom)

I saw an ant in the bathroom a few weeks ago. I said, EW and stomped it so it wouldn't bring its friends. Well, I think they found out and are getting their revenge! I have a trail of ants in the bathroom/laundry room and no clue or idea how they are getting in. I put down ant poison and am keeping the door closed to keep Ian and the cat out but since I put the stuff there now I have even more ants! I guess it must take some time for the ants to take the poison to their nest or whatever but in the meantime I hate going in there. And I have to have a shower later! Ew! Here are some pics: