If you’re in the market for some weekend sleuthing, here’s a Scooby snack for you: For the last year or so, a bizarre YouTube channel has been posting thousands of odd abstract videos, prompting wild speculation from conspiracy theorists online.

Then — just this week, actually — the channel abruptly and mysteriously disappeared.

According to multiple online reports, the channel previously known as “Unfavorable Semicircle” began posting videos last April. At first, the brief abstract videos appeared to be some kind of automated test transmission — perhaps similar to the similar Webdriver Torso account mystery. (That account turned out to be an internal testing utility used by YouTube engineers.)

YouTube Launches Eyewitness Video ‘Newswire’

But around eight months ago, videos began appearing with an encoded audio track that’s since been dubbed the Voice. In clips featuring the Voice, a man can be heard reciting strings of letters and numbers — or sometimes a single letter or number. Other videos featured odd visual patterns and seemingly random arrangements of dots against a field of solid color.

Most clips only last a few seconds, but two run much longer and they’re the ones that have conspiracy theorists intrigued. Labeled “Lock” and “Delock,” the longer videos feature intense flashing colors and warped, highly processed audio. Invariably described as “disturbing” and “unsettling,” the tracks include ambiguous sounds that some claim are people whispering or children singing.

NASA: We Need YOUR Help to Solve Ceres Mystery

Creepy, right? Unfortunately, the YouTube channel has been deactivated with an onscreen message reading: “This account has been suspended due to multiple or severe violations of YouTube’s policy against spam, gaming, misleading content, or other Terms of Service violations.”

If you want to dive down the rabbit hole, an ad-hoc investigative team of Reddit users has assembled a database of the roughly 10,000 (!) video clips uploaded in the last year. Unfortunately, as of now, all links to the original YouTube postings are broken, due to the account being deactivated. Some users are posting zip files with copies of the videos. Download at your own risk.

So what is Unfavorable Semicircle? A viral marketing stunt? A numbers station? An underground indie game? The investigation continues. Let’s split up — Shaggy, you go with Velma.