Between Lehko's candle, Jerek's rope, and Kuma's anchorage, Ydyr manages to clamber out of the pit--really, more of a hollow in the loose stone flooring--without mishap. Heirmund keeps alert, but sees no signs of rats, as the others quickly make their way back into the room without being attacked, despite the growing chittering and squeaking Ydyr's fall stirred up.
You vacate the nest room just in case, shut the door, and organize yourselves in the fountain room. Once you are ready, you backtrack southwards to examine the rooms you passed on the way in. The first doors you check are the six doors in the hall leading to the fountain, which you had shut just a few minutes earlier to keep any potential rats from attacking you. A quick, cautious look in each of these small rooms shows nests with varying levels of filth, unoccupied and with no other exits.
Just past that hallway, you find the second door waiting for you, leading west. Jerek carefully examines the door and finds no traps, so Kuma opens it--to find a 20' square room empty of anything, except only rat droppings, crumbled flagstones, some minor stains, and another door leading out to the north. Jerek checks that door, and finds no traps as well, so Kuma opens it--to release a loud clangor of bells, struck by the door as it swings open!
The 10-foot-wide hall revealed is liberally strewn with sharp caltrops. The northern door 20' away to the north is missing, but the room beyond is partially blocked by a roughly-mortared 3-foot-high wall, complete with crenellations.
((Jerek's search check: 9+6=15.))