At last, Rufus Norris’s National Theatre has come of age. `

Breathtaking, brave and brilliantly acted, Downstate is a landmark play. It’s listed as a ‘collaboration’ between NT and Steppenwolf, but the Chicago company’s prints are all over this glistening weapon.

Sometimes a play is just arrestingly good. Sometimes it’s also amazingly timely. As the creative legacy of Michael Jackson is re-examined in the shadow of fresh allegations of paedophilia, it’s sensational that the National Theatre should present a piece – by Pulitzer-winning Bruce Norris, author of Clybourne Park – which is not entirely condemnatory of the ankle-tagged offenders who have fetched up in a charitable co-living house in rural Illinois.

Script and acting combine to normalise the characters: could Francis Guinan’s sweet old wheelchair-bound grandpappy Fred really have been the virile young music teacher who taught his underage pupils a special type of fingering? When Tim Hopper’s excellent clockspring-wound insecure Andy comes to confront his abuser with a contract of closure designed by his therapist, he’s almost beguiled by the gentle self-effacement of a man of whom he was once terrified. Matilda Ziegler as his hardboiled wife is most definitely not.

The acting is universally splendid, every character has immense depth and credibility developed by Steppenwolf technique, but Bruce Norris’s script constantly defeats stereotypes and predictability. The way the characters establish a pecking order for household chores based on the comparative severity of their crimes is insightful and thought-provoking. You will leave this play wanting to talk.

Cecilia Noble’s coffee-mug toting Ivy may start as an amiable wisecracking black woman who wouldn’t seem out of place in Waitress or Hairspray but reveals solid police skills when the situation changes. But it’s K Todd Freeman’s ex-choreographer Dee, who loved the young chorus boy he dated for five years before being arrested – that most engages you, and carries you with humour and fierceness through the storylines until he eventually, gently, and beautifully breaks your fucking heart.

When I first started going to the theatre, you didn’t even see homosexuality on stage – not until 1970 when The Boys in the Band broke new ground by showing gay characters with a backstory, and started a slow landslide towards acceptance and understanding.

Downstate could just be the starter of a new avalanche.

In a word, it is unmissable.

Until 27 April