Unneeded stress

Yesterday, while I was getting ready to go to the bar, Brian, who lives below me phoned and said that there was a leak around his living room window. I checked my window, and nothing similar was happening to it.
Today, I noticed that the carpet around that window was moist. I looked under the bookcase at the wall and there is something green there, possibly growing. I’m taking this as a bad sign.
Stress level rising.