Every campus has its little mysteries. The vending machine that eats dollars on the third floor of the science building. The door that's always locked but never leads anywhere. And at one Minnesota college, until recently, there was the matter of the mystery liquid that kept turning up on students' belongings, a slow-drip serial nuisance that nobody could quite explain and most people probably tried very hard not to think about.

According to records obtained and reported by MSN, the explanation turned out to be worse than anyone's most aggressive not-thinking-about-it. A professor at the school allegedly urinated on a student's backpack, and when the incident was investigated, the trail led back to him as the source of a whole series of similar, um, spillages around campus. The serial sprinkler had a name, a title, and presumably tenure review materials somewhere in a filing cabinet.

I want to be clear about what draws me to a story like this, because it isn't the gross-out factor. Well. It isn't only the gross-out factor. It's the structure of it. This is a closed-circle mystery in miniature: a pattern of unexplained phenomena, a period of innocent theorizing (condensation? A leaking pipe? A very unlucky backpack?), and then the reveal that the answer was a human being making choices. The most mundane possible culprit, which is exactly what I said last time I wrote about one of these internet whodunits, and it keeps being true. It's almost never the supernatural. It's almost always a guy.

The records describe the incident with the flat administrative tone that these documents always have, which is part of what makes them so unsettling to read. What gets me is how bleak it is that a serious institutional document has to describe, in careful neutral language, the deliberate placement of urine on a student's property by a member of the faculty. Somewhere a human being typed those words into a form. Somewhere a review board read them out loud. These are the unglamorous rooms where strange stories actually get processed, and I've spent enough nights in the weirder corners of case files to know the tone by heart.

The details available are sparse, as they usually are while personnel proceedings grind along. The professor's name, the school's handling of it, the student's side of things, all of that sits behind the usual privacy fog. What we have is the shape of the thing: a pattern, an incident, a match. The pattern was noticed only after the incident, which is how patterns usually work. Nobody connects the damp backpacks until someone catches the sprinkler mid-sprinkle.

And that's the part I can't stop turning over. For however long this was allegedly going on, there was a period when the campus just... lived with it. Students wiped things off. Maybe somebody complained about the plumbing. The unexplained liquid was a background condition of campus life, the way the Taos Hum is a background condition of Taos, the way that low-frequency drone I wrote about a while back is just something certain people learn to sleep through. We are astonishingly good at normalizing the weird when the weird arrives quietly and in small volumes. It takes a caught-in-the-act moment to retroactively transform months of minor inconvenience into a story with a villain.

The university hasn't, at least in what's been reported so far, said much beyond what the records force it to say. More may surface. These things tend to, slowly, through the same records pipeline that cracked this one open, and if it does I'll be here, because a follow-up about how an institution explains its own serial sprinkler is exactly the kind of dry, quietly horrifying paperwork story I can't leave alone.

Sleep well. Check your backpack.