It is confirmed that Joey has inherited demonic powers from his father.
This is the first episode to feature a non-demonic enemy.
We learn the demon that killed Helen Baxter was called Asmoth.
The characters of Jamie and Zoe are named after two of the Doctor's companions in Doctor Who.
The word banshee is derived from the Irish bean sidhe, a wailing woman whose cries warn of a death in the household. If caught, she will name the person to die.
The Banshee reveals herself to be 532 years old.
We never discover who or what was talking to Liam in the mini-cab: was it the ghostly voice of Dean McGrath?
John tells Jude that the wounds which appear randomly and without warning on his back were left by a demon he was pursuing in connection with the deaths in 1999.
The tattoo on Billy, Jason and Matthew depicting a sword in flames is the symbol of Kaa-Jinn.
Jude doesn't work on Tuesdays.
The Demonica Diablo is destroyed in this episode.
Doddington is documented as having a Cliff Richard collection.
We learn for the first time of John's connection to the death of a woman named Helen Baxter in 1999.
The large tome Black is withholding is called the Demonica Diablo, a sort of encyclopedia of all the demons and other such creatures who roam the Earth.
Rich/Azal was apparently partly responsible for the discovery of electricity.
Strange indicates that demons who roam the Earth appear only in human form.