Complex sentence: Detective Inspector John River is haunted by visions of his recently murdered colleague, Detective Sergeant Jackie'Stevie' Stevenson, and attempts to find her killer despite his exclusion from the case on the grounds of his proximity to the events surrounding it.
Split into simpler sentences: Detective Inspector John River is haunted by visions of his recently murdered colleague, Detective Sergeant Jackie'Stevie' Stevenson. He continues in his attempts to find her killer although excluded from the case on the grounds of his proximity to the events surrounding it.