Entity: Book 1 of The Demons Among Us series

When Terry Robertson was a child, he watched helpless and terrified as a demon possessed his little sister, eventually ending her life, despite help from multiple exorcists. He vowed from that moment on that when he was older, he would devote his life to finding the demon that destroyed her and banish it back to hell. And the demon has a name.
Ba’al.
Pete and Janet Henderson move into their new home with their 9yo son, Danny, happy to start over again after a fire burns down their previous home. But things soon start going wrong. Danny wakes up in strange places, even outside when all doors and windows are locked, inexplicable nosebleeds as does Janet who is also seeing terrifying shadows in the house.
They soon realise it’s not a doctor they need but someone else. And that someone is ready and waiting…