Watch the trailer for HBO's Tickled, a documentary about 'competitive tickling' that gets surprisingly dark

Driven to delve deeper, Farrier uncovers a bizarre world of fetish porn, manipulation, money and criminality in the documentary.

When he asked for a simple interview with the company behind it however, he received a blistering, homophobic and threatening response.

With humor and determination, Farrier and co-director Dylan Reeve summon up every resource available to get to the bottom of this tickling wormhole.’