mold behind drywall near plumbing 28

https://storyquanta.com/s/R61e3zgXlsDvT8MR9iMoz

Peeling wallpaper and a faint musty smell tipped me off, so I cut a small hole in the drywall near the bathroom sink. Behind it, black mold was spreading along the plumbing, probably from a slow leak that'd been going on for months. The insulation was soaked.