Wet coming up on hardwood

My boyfriend and I just bought a 1910 house. We did this actually
expecting a LOT of work, but this has us scratching our heads:

We spent part of the weekend ripping up carpet, because it smelled of
urine. Of course, we found urine/water stains on the hardwood -- we
expected that, and are going to deal with it. The thing that has us
stumped is, yesterday, we found the stained areas, which had been dry the
day before, suddenly wet, in some places with pools of dark liquid. Does
anyone know if this could be the urine/water rising from the floor, or
something else? (I know there was a horror movie that started this way,
though I am not seriously going there!) The basement under the floor is
unfinished, and there is no visible leak, nor a water source handy. The
radiators are off, and the only one of those with any real issues is two
rooms away, on an exterior enclosed porch!

Any wild guesses, expert diagnosis, general sympathy welcome! Thank you
all so much in advance.