What we noticed first was a small leak under the stove. Then it disappeared. Next, there was a slight swell to some boards, but not enough to notice. Then one day, we walked into the kitchen, and there was a "holy cow!" moment as we realized there was a big hump in the floor, and that immediately above the tub in the basement was a spreading stain of yellow with a moldy spot in the center.

Yep, we had a leak.

Yeah, I have not seen this kind of cable for ten years. Seriously, the last time was when I was working for Las Vegas Computers, circa 1997 or so.