That’s our living room ceiling, right under our bedroom radiator. Water was slowly dripping out of that crack.
It had sprung a leak overnight during a polar vortex, so basically the heat almost never shut off and the water dripped, dripped, dripped while we slept. We got the name of a good emergency plumbing/heating place who sent a great guy out the same day (we weren’t about to mess around with a DIY attempt when it was zero degrees and a holiday weekend looming). It was a quick fix and he had all the spare parts we needed in his truck, so it all worked out fine. And while assessing the ceiling damage we realized there was the shadow of a much larger patch and crack there - this had happened before, much worse. Knowing the history of how things were done in the house, the previous fix had been a cheap patch job that created a ticking time bomb we didn’t know about.
All other radiators have since been checked and two others were fixed - the one in the playroom had the same problem and another with a totally different issue (it wasn’t getting hot anymore so it was nice to have that fixed). Since then we haven't seemed to have any more problems, and hopefully one of these days things are going to warm up... though I'm not holding my breath because last year spring didn't show up until the very end of April and it was torture.
Now the ceiling looks like this. We need to patch it but we wanted to give things some time to dry out and then we’ll assess what we need to do. For now the ceiling is held together with drywall tape. It actually looks worse now because the original patch (done with paper!) started to curl as it dried. I'm also a little nervous because I have no clue what shade of white paint the ceiling is. After we patch there's a very good chance we'll have repaint the whole thing and that's a huge job with all our furniture...