Based on an idea creator Chris Lang has been working on since the 2016 Brexit referendum, the new season sees Jess and Sunny investigate when suspected human remains are discovered on Whitney Marsh.
It soon becomes clear that the remains are relatively recent and that the body has already been dismembered there.
Meanwhile, we meet outspoken TV commentator Melinda Ricci, Martin 'Marty' Baines, an autistic man living with his mother, Asif Syed, an Afghan training for his citizenship test in Britain, and history teacher and head of faculty Juliet Cooper.
Jess, Sunny and their team must unravel their connections to uncover the truth.
The cast for the season has also been revealed, with Victoria Hamilton, MyAnna Buring, Jan Francis, Damien Molony, Max Fairley and Elham Elas joining this year's guest cast.
Jordan Long, Carolina Main, Pippa Nixon, Georgia Mackenzie, Andrew Lancel and Kate Robbins return in their supporting roles. Lang will write the new season, while Andy Wilson returns as director.
Keenan said of returning for season 6: "I am absolutely delighted to be stepping into the world of Unforgotten once more. "To be involved with the incredible team at Mainstreet on yet another set of stellar scripts from Chris Lang, with the brilliant Andy Wilson at the helm, is a real treat. "And to get to work again with Sanjeev, Carolina, Jordan, Pippa and Georgia is an absolute joy. To call it work is a total misnomer. I can’t wait to get started!"
Bhaskar added: "I’m humbled and excited to be back as Sunny Khan, bearing the backpack for series 6 of Unforgotten. "Chris’s scripts, as ever, are intriguing, detailed and empathetic. Andy’s direction and the skill of Sinéad and the cast make this a warm and creative experience that [is] so much more than a job. Once again I feel lucky to be a part of it."
Meanwhile, Lang said: "I'm incredibly excited to be about to start filming the sixth series of Unforgotten, with a story that has been gestating for nearly eight years, since 23rd June 2016, when our country seemed to fracture in two. "The UK, and indeed the world, has today never seemed more divided, and series six attempts to try and understand how we got to where we are now and, perhaps more importantly, where we can go from here."
