To stop the first leak, I cleared the gutter on that end of the house (yes, in the pouring rain). I suspected a clogged gutter because, 1) (ahem) it was clogged, as evidenced by the overflowing water; and 2) a similar problem with the front gutter had caused a similar wetness on another part of the ceiling as water found its way under poorly fitted roofing-to-wall joints. *sigh*
To discover the other leaks, I climbed into the extended section of the attic (remember my "secret room"?) to see if I could find the source - and identified a leak in the chimney siding (yes, it was built for crap). I'll have to seal that when the siding dries. Or maybe just refinish the house's siding properly... when I stumble upon a suitcase of cash. Couldn't find the other leak (surely hidden above the new roof-insulation I installed in the spring), so I guess I'll just have to climb up onto the roof and squirt sealant underneath the flashing that joins the two roof peaks. When I can use my shoulder again, that is.
Which leads to a moment of low comedy. Getting back out of the attic's secret room was... something else. See, it has a sloped floor on both sides, which is also the cathedral ceiling of the living room, aka "gaming room." The room is about 14 feet long, but width and height vary from 3 to 8 feet depending on the slant of the roof, the ceiling beneath, and how the compound angles join. See exhibit below.
Exhibit A: The Secret Room Prior to Insulation-ing
I know I have photos of Mike, Matt, and myself insulating this space - buried in blown and sheet fiberglas, sweating our brains out in long sleeves inside that oven (now comfortably insulated, thank you, Mike and Matt!) - but can't seem to locate 'em. Anyhow. To cross to the side by the chimney (that's the steel tube hanging out inside that out-thrust section of wall), one must clamber over the peaked top of the ceiling below. It's simpler now, because I installed plywood on this side to make the space usable and 2x4s on the other side to act as steps, so getting over wasn't difficult. However, with my shoulder messed up and not able to bear much weight, getting back across the peak was... interesting.
The journey was partially successful, in that I discovered the leaky chimney-siding, but partially unsuccessful in that I couldn't pinpoint the roof leak.
Rain has stopped, thankfully! May your domicile be rain-free (inside, anyway).