DI Jen Flowers thought she'd seen it all after fifteen years on the force, but when a vigilante serial killer hits the city and uses social media to gather supporters, she must fight the public and her doubts to catch a murderer and save her daughter.

Suffering from blackouts and abandoned as a child by her father, Ruby Vasquez has been chasing that one scoop to make her an internet star. Living with an alcoholic mother who hates her, Ruby discovers a secret about the vigilante's first victim, which puts her in the killer and DI Flowers' sights.

Jen and Ruby have to overcome the secrets in their past while battling each other to discover the Hashtag Killer's identity. Jen will have to choose between keeping her daughter safe or finding a killer, while Ruby will need to decide if becoming famous is more important than doing the right thing.