Lovesong, Lyric Hammersmith, London Huis Clos, Trafalgar Studios, London Man in the Middle, Theatre 503, London

An elderly couple and their younger selves dance towards death in a moving tribute to enduring love

Elderly Maggie opens her wardrobe door and a young woman sashays out. For a while, family life in Lovesong seems frightfully overcrowded, resembling a game of sardines, or perhaps the more recent and widespread Kippers – as in Kids In Parents’ Pockets Eroding Retirement Savings.

In fact, in Frantic Assembly’s romantic tragedy – which premiered in Plymouth and combines modern dance sequences with a script by Abi Morgan, screenwriter of The Iron Lady– the domicile is sadly childless and haunted by memories.

Now terminally ill, Siân Phillips’s Maggie (a Mrs Alton, not Mrs Thatcher) is quietly distressed as she attempts to countenance death with dignity. Her husband of 50 years, Sam Cox’s Billy, is supportive yet struggling to cope as he realises Maggie’s bottles of pills can’t stave off the inevitable for much longer.

Their home is impressionistic: angled slivers of a sunlit wall, a double bed and kitchen table amongst fallen leaves. And time is open-plan here, too. As Maggie and Billy remember their early married life – its passionate and rocky patches – their present and their past selves (Leanne Rowe and Edward Bennett) weave in and out, sometimes dancing ardently across the age gap, swapping partners.

The choreography (by directors Scott Graham and Steven Hoggett) is hit and miss. Technically it lacks polish, as these actors were not born to dance, but they’re admirably game. It’s not often you see a senior citizen held aloft and spinning on a thirtysomething’s shoulder – and vice versa. Other inspired moments include Billy suddenly dreading bereavement, reaching into the fridge for a stiff drink, and finding his young bride tumbling into his arms – part lover, part corpse.

Morgan’s script, alas, sometimes lapses into the corny, and the multimedia production layers on the sentimentality, with soft-focus projections of conjoined hands. Nonetheless, this portrait of ageing and enduring love tugs at the heartstrings, whatever your date of birth.

In Huis Clos (aka No Exit), written by Jean-Paul Sartre in 1944, a trio of damned souls find themselves stuck in an afterlife where there’s no need for old-school fire or brimstone. Garcin (a murdered radical journalist), Ines (a lesbian postmistress) and Estelle (a high society femme fatale) are locked in a room together, for eternity, and soon fall to tormenting one another, leading Garcin pithily and famously to conclude that “Hell is other people.”

Yes, three is an infernal crowd, and Paul Hart's staging – in a mini-season promoting young directors under the Donmar's banner at the Trafalgar Studios – scores top marks for claustrophobia. The audience is crammed, cheek by jowl, into a tiny basement auditorium, hemming in the actors on every side.

Moreover, Will Keen's Garcin is riveting. He's the first new resident to be ushered – by a subtly sardonic valet (Thomas Padden) – into Sartre's gilded but mouldering chamber (as designed by Lucy Osborne). Garcin is trying to keep cool and calm, with with his pencil moustache and buttoned-up suit. But you can almost smell the fear and vexation oozing from every pore as he asks, tersely, where the expected red-hot implements of torture are kept, and if he's going to be given a toothbrush, since he's going to be staying for ever.

Unfortunately, after that grippingly tense start, hell proves little more than a mild bore. Some teasing questions are raised about guilty consciences and free will as the threesome create a sort of self-service perdition, but Sartre was not a great playwright. Huis Clos's plot twists – developing a love-hate triangle – no longer seem fiendishly clever or even startlingly boho. Indeed, the permutations of these power games now come across as schematic and repetitive.

Though Hart's casting is strong, Michelle Fairley's vociferous, man-hating Ines is somewhat wearisome, with a well-to-do English accent that diminishes the class tensions. Fiona Glascott's Estelle, meanwhile, strikes her vampish poses a tad stiffly, not helped by having to get down and dirty with Keen while draped over an awkward wooden chair. Keen is far more electrifying when his temper snaps and he becomes a blur of quivering rage, hammering at the door and yelling to be let out.

In Ron Elisha's biodrama Man in the Middle, WikiLeaks's editor-in-chief, Julian Assange, played by Australian actor Darren Weller with scruffy ash-blonde hair and a juvenile streak, presents himself as an internet freedom fighter. Having acted as a conduit for whistleblowers to expose the dirty dealings of global leaders, we see him being vaunted as a revolutionary journalist, crusading for transparency, and being nominated for a Nobel Peace Prize. Of course, he ends up facing trial in Sweden on charges of sexual assault, which, he insists is a political stitch-up. Some in the United States, we are told, want him extradited there, to face a death sentence.

Assange is a fascinating subject, and naturally Elisha wants his protagonist – hero or antihero? – to remain a complex, ambiguous figure. Fair enough. However, Man in the Middle is a mess of scrappy biographical bits and bobs, the dialogue mostly feeble jokes and laboured epithets ("a geek with a leak, a doubter with a router" is not the worst of them). Director Lucy Skilbeck's London Fringe premiere boasts a glossy black set with sliding screens. But Ben Onwukwe's portrayal of a furiously effing Barack Obama and Jonathan Coote's farcically grinning David Cameron are barely recognisable.

This story surely ought to make credible drama, at the very least. Instead, it blithely declares itself to be a blend of "uncovering" and "imagining", and hopes to get away with reflecting merely the slipperiness of a man who, while advocating the naked truth in politics, used to go by the name of Mendax – the Latin for "lying".

'Lovesong' (0871 221 1722) to 4 Feb, and touring to 18 Feb; 'Huis Clos' (0844 871 7632) to 28 Jan; 'Man in the Middle' (020-7978 7040) to 4 Feb

Next Week:

Kate Bassett unpacks Travelling Light at the National Theatre, with Antony Sher on board

Theatre Choice

Mike Leigh's Grief back at the NT (to 28 Jan), is a quietly satirical, then heartbreaking portrait of single parenting and teenage surliness, with Lesley Manville in 1950s suburbia (day tickets and returns only). Fog is a potent new play about a feckless white youth on a housing estate: an impressive fringe premiere at London's Finborough (to 25 Feb).