Kevin works as Canon Black's gardener which is very convenient because he's able to spy on the Canon and find out various things as he peeps through the window pruning the hedges.
The other thing about him is that as he's a Down's Syndrome person the Canon presumably doesn't even conceive he could possibly pass on information. Kevin is also super-sensitive which means he also picks up demon vibes and is often the first sign that something demonish is about to happen in the vicinity.
What can you tell us about Joey?
Joey is the son of Jude and Rich, who turned out to be the demon Azal in episode one. Doctor Who fans may possibly recognise that name. There are little Doctor Who references sprinkled throughout the series. See if you can find them.
Is that why there are two hunt saboteurs called Jamie and Zoe?