That September date might change, because, as I recall, last season, each episode was available in the USA within 24 hours after it aired in the UK. I don't think the BBC wants one of its hottest exports pirated before making its official, legal debut Stateside.
I made an inquiry on all that, so when I get a response from the BBC, I'll share here.
Here's what's coming this season:
Luther returns to investigate a twisted fetishist who is murdering women in a horrific echo of an unsolved case from the 1980s. The team must put all their resources into finding the copycat killer, whose murderous spree has only just begun.
Luther’s focus is divided when a reluctant Schenk assigns him to another case – a malicious internet tormentor has been found murdered in his home, with all his possessions stripped from the flat. With so many people wanting the tormentor dead, Luther needs to apply brute force to a key witness for more information, unaware that every move he makes is being watched.
Pulled in every direction, Luther’s patience is wearing thin and a car crash, as he rushes to the second crime scene, is the last thing he needs – or so he thinks, until he sets eyes on the beautiful Mary Day. Could this chance encounter mean that Luther might just be on the verge of finding love?
But nothing ever comes easily for John Luther and other forces are at work against him, in the shape of Erin Gray, now a DCI in anti-corruption, and her boss, DSU Stark. Stark and Gray will stop at nothing to punish those who work outside the perimeters of the law and their furtive plan involves the man who is Luther’s colleague and best friend – DSU Justin Ripley.
DCI John Luther is played by Idris Elba, DSU Justin Ripley by Warren Brown, Mary Day by Sienna Guillory, DSU George Stark by David O'Hara, DS Erin Gray by Nikki Amuka-Bird, DSU Martin Schenk by Dermot Crowley and Benny Deadhead by Michael Smiley.