Sheridan Smith and Stephen Merchant will play in a new BBC drama about Stephen Port's murders.
The Barking Murders are narrated from the perspective of the families of the victims and focus on their struggle to uncover the truth about what happened to their sons and brothers.
The serial killer stunned and raped young men before dropping them near his home in Barking, East London.
The watchdog of the police is investigating whether charges of serious misconduct should be made against the officials involved in the investigation, through which Port could slip through the net.
The three-part fact-finding drama is written by Jeff Pope and Neil McKay, who were responsible for The Moorside and Appropriate Adult.
Merchant will play Port, while Smith Sarah Sak, the victim's mother Anthony Walgate, and Jaime Winstone will play Donna Taylor, one of the sisters of victim Jack Taylor.
The trader said, "This story can not be ignored – how four young lives were lost and the courageous attempt of their families to uncover what happened.
"This factual drama will shed light on their story, so it's a privilege to be in with the brilliant combination of Jeff Pope, Neil McKay and the BBC."
Smith added, "I love to play real characters – especially an inspiring woman like Sarah Sak – but that brings responsibility.
"Together with the other families, Sarah had so much heartbreak and it would have been easy for her to just accept what she was told by the police, but something made her keep fighting for her son."
McKay said, "Four young men whose full future lies before them died in a brutal and tragic way.
"This is not just a story about the consequences of this loss, but also about the extraordinary courage and resilience of those who loved them as they sought for truth and justice. It is a privilege to tell. "