Voices from Beyond — Simon R. Green

Meet the operatives of the Carnacki Institute -- JC Chance: the team leader, brave, charming, and almost unbearably arrogant; Melody Chambers: the science geek who keeps the antisupernatural equipment running; and Happy Jack Palmer: the terminally gloomy telepath. Their mission: Do Something About Ghosts. Lay them to rest, send them packing, or just kick their nasty ectoplasmic arses…

In a quiet London suburb, four university students participating in an experiment inside a reputed haunted house hold a séance that goes terribly wrong. What -- or who -- ever they summoned has taken their minds away, leaving them empty shells.

Enter the Ghost Finders, ready to confront an enraged poltergeist for the students' very souls.

All in a day's work -- except the team doesn't know that in another part of the city, a different entity has also breached the threshold between worlds. And this time what is at stake is not four lives -- but the very existence of all humanity.