Demon Dagger

Drew Price has a gift, or perhaps a curse.
When a demon possesses a person, Drew can see the horrific-looking demon that dwells within. This ability has made him a demon hunter, armed with the one weapon that can send these fiends back to Hell; the demon dagger.
A demon named Nicobar sets its sights on punishing this hunter. It starts by taking the soul of Drew's son, condemning the boy to life as a psychopath.
This fast-paced, chilling novel follows Drew's attempt to save his son's soul and then use the blade to end Nicobar's time on Earth.