Now streaming on Paramount Plus, criminal minds evolution.

All my years as a profiler I studied killers, but I never studied what a pandemic would do to them.

We started communicating to become better predators.

The deeper you dig.

These aren't just connected cases.

This is a serial killing network.

The darker it gets.

There isn't enough time.

It's not over.

We're just getting started.

Criminal minds evolution. Stream new episodes now. Exclusively on Paramount Plus.

Something pretty disturbing happened in Circleville.

Starting small and flourishing over decades.

Residents began to receive letters.

They accused the citizens of being involved in some pretty terrible things.

Embezzlement, domestic violence, affairs, and even murder.

The Circleville letter writer knew everything about everyone and knew everyone's secrets.

They were vicious.

And ugly, somebody with some severe psychological problems I would hazard to guess.

The threatening anonymous letters kept coming.

Hundreds of them.

Most were postmarked from Columbus, Ohio about 30 miles north, which is where I grew up,

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