The series follows the residents of Sinkhill, a 'forgotten East End district of a warped funhouse mirror vision of Glasgow, Scotland'; a place where crooks, deviants and killers as well as the ordinary folk unfortunate enough to live among them reside.
Sink contains examples of:
- Affably Evil: Si McKirdie runs most of the organized crime in Sinkhill but can be fairly charming and easygoing as long as you're on his good side.
- Beauty Is Never Tarnished: Subverted with Charlotte in #6; the clowns give her a Glasgow Grin as well as a clown nose that is forced onto her with needles on the inside.
- Driven to Madness: The clowns spray some sort of gas on their victims to drive them insane and induct them into their group. One woman manages to escape this ritual but is implied to have been driven insane from the experience nonetheless.
- Facial Horror: The clowns have hideous Glasgow Grins as well as red noses that are attached to their faces via spikes on the inside.
- Monster Clown: A blue van filled with psychotic clowns drives around at night. Those unfortunate enough to be caught by them are mutilated, driven insane and turned into clowns as well.
- Pet the Dog: A literal example with McKirdie. After a young girl's dog is killed for 'bait' as part of a dog-fighting ring, he breaks up the operation and gives her an abused fighting dog to look after.
- Shovel Strike: Mr. Dig's weapon of choice is a shovel.
- Vigilante Man: Mr. Dig is a fox-masked vigilante who dishes out his own brand of justice on those unfortunate to cross him.
- Wretched Hive: The titular Sinkhill is this on its good days.