Fram, NT Olivier, London<br />Small Change, Donmar, London<br />Hapgood, Repertory Theatre, Birmingham

Tony Harrison's story of explorer Fridtjof Nansen is in verse but, despite an excellent cast, it's poetry in slow motion

The National Theatre is in love with biodramas this season, but will its audiences be so enamoured? Last month saw the premiere of Howard Brenton's portrait of Harold Macmillan, Never So Good, which could have been better. Now, penned in verse by another veteran writer, Tony Harrison, we have Fram, the saga of Fridtjof Nansen (1861-1930), Arctic explorer-turned-League of Nations figurehead for Norway.

Great Scott, this is tedious! We are repeatedly told that Fram – the name of Nansen's boat – means "forward", yet the play itself has no momentum. Co-directed by the dramatist and set designer, Bob Crowley, it's a disappointing scrappy mess. Its only steering capacity appears to be giving a wide berth to any potentially engaging human relationships that hove into view.

The dramatist piffles around with a long prologue, conjuring up the wearisome ghost of Gilbert Murray, another league member and a B-rate translator of Ancient Greek tragedies. Harrison is pretending that Murray has written Fram – as if that'll let him off the hook.

When we do eventually find ourselves in the Arctic with Jasper Britton's sniffy Nansen and his uncouth fellow-explorer, Mark Addy's Johansen, they are stuck on the pack ice. Their tiffs about a farty sleeping-bag and Nansen's arty taste for poetry are going nowhere either. Harrison's own rhymes descend into feeble doggerel here.

After a bewilderingly unintegrated ballet comes a clumsily handled debate about the use of film or theatre to shock people into donating to famine relief. Harrison's worries about whether the arts or peaceful cooperation can save mankind from atrocities or an apocalypse are peculiarly garbled. The cast does its best, with sheer gusto, but I'm afraid it would be charitable to hoist Fram out of the repertoire ASAP. Why not give the price of a ticket to a better cause or head for the Donmar?

Peter Gill's chamber piece, Small Change – revived by the dramatist-director – is a memory play with an understated element of autobiography. Matt Ryan's Gerard is a highly strung writer. He steps back into the past, reliving his childhood in working-class Catholic Cardiff, obsessing over two bonds of love: one with his no-nonsense but covertly tender mother (Sue Johnston); the other with the lad-next-door, Vincent (Luke Evans).

Gill's staging has exquisite simplicity: a line of wooden chairs, twisted at different angles. Just by leaning away or towards each other, the characters can switch between isolation and communion, internal monologues and conversations. Some lines of thought break down, poetically, being left unfinished. Others are repeated as if on a loop tape. Small Change explores the nature of remembrance, love and grief and why we can't let go.

Ryan is particularly scintillating and should be a major star. He captures childishness with amusingly small adjustments, is emotionally mercurial with fierce explosions of bitterness, and has a flawless sense of musical pacing. Perhaps Lindsey Coulson, as Vincent's insecure mother, could be more intense. However, her scene with Johnston's supportive Mrs Harte – when they dance together and don't care who sees – is unforgettably touching.

There's also a chance to catch a rarely seen Stoppard play, Hapgood (1988). In spite of rewrites, this serio-comic Cold War spy thriller remains convoluted. I struggled to follow the unbelievable shenanigans of Josie Lawrence's Secret Service chief and her inner circle. They are intent on skewering a double agent in their midst, or maybe it's two or four or more double agents ....

Anyway, too tricky is better than boring. This play is espionage's answer to The Comedy of Errors, with multiplying identical twins. Stoppard draws comparisons between human duplicity and quantum physics too. The science isn't as wonderfully integrated as in Arcadia. However, Hapgood is intriguing and entertaining, and Rachel Kavanaugh's production is pretty slick. Christopher Ettridge, who plays Hapgood's right-hand man, deserves a special mention. At the performance I attended, he soldiered on after passing out on-stage, suffering from arrhythmia of the heart – a chilling moment when it dawned on the audience that he wasn't pretending.

'Fram' (020 -7452 3000) to 22 May; 'Small Change' (0870 060 6624) to 31 May; 'Hapgood' (0121 236 4455) to 26 April