Alison is recovering from the traumatic séance that saw her inhabited by the ghost of Robert's son, and realizes she has to dedicate her life to helping spirits. After seeing a strange woman at a roadside, she becomes embroiled in the mystery surrounding a fatal car crash.
Alison and Robert investigate a series of suicides in a prison, where murderer Ian Garland claims a malevolent spirit called the Rat Man urged him to commit multiple crimes. Alison is soon convinced the ghost is responsible for the deaths and tries exorcise it from the place to help the other convicts - but endures terrifying visions of the killer's victims in the process and puts herself in terrible danger.
Alison is contacted by a father who has heard a voice whispering to his infant son through the baby monitor, as she struggles to deal with being haunted by her own mother's spirit. The child's mother refuses to heed the medium's warning to leave the house and becomes convinced her husband is going mad. Meanwhile, Robert confronts his long-buried feelings for Jude - before receiving some shocking news
Alison investigates when Lucy, a bride-to-be, starts exhibiting symptoms of the skin disease that killed her husband Jonathan's first wife, and realises the bride is possessed by the dead woman's spirit. Meanwhile, unaware of Robert's illness, Alison struggles to understand his sudden scepticism as she also struggles with the ghost of her dead mother - who is beginning to take over her life.
Alison attempts to intervene when the ghost of a man who killed a student starts to haunt the dead girl's best friend - who clearly knows more about the spirit than she is letting on. As the medium becomes more erratic, Robert starts to fear his friend will end up the same way as her mother, but fails to convince Alison to talk about her increasingly odd behavior.
As Alison gives in to the madness induced by her mother's spirit, Robert tracks down the medium's estranged father, hoping he will provide an explanation for his daughter's haunting. The trio spend a stormy night dissecting the secrets of the past - leading to revelations about Alison's childhood and how her mother died.
Alison investigates when a teenager who has been haunted by visions of a young boy claims the psychic he has been visiting is an impostor, but finds herself unable to connect with the spirit world. While Robert reassures his colleague that she still can use her insight into human emotions for the benefit of others, he struggles to find the right moment to tell her the news about his failing health.
Alison launches a frantic search for Robert after being shocked by a terrifying vision of him. She eventually bumps into Barbara, who reveals the lecturer has been admitted to intensive care. Sitting at his bedside, the medium detects the spirit of a nurse who has made it her mission to try and care for every patient admitted to the hospital.