In a collection of tents beneath a railway arch, three homeless people spend the night.  Gentle, thoughtful Ebi used to be a plumber, while the combative Bess is clearly leader of the gang; the trio's completed by Hannah, who ran away from a broken home and whom Bess seems to have taken under her wing.  It's a night like any other, a night the three friends live through again and again… except that on this night, a stranger, Caz, suddenly appears on the scene.

On one level, Kings is a tense and nuanced character study, focussed on the treacherous and ambiguous alliances so often forged from necessity.  Bess, Ebi and Hannah seemed happy enough before Caz arrived; but as the newcomer imposes her own will on the group, fractures develop along unexpected lines.  Some of the old friendships are more opportunistic than they seemed, and important secrets have been left untold.  By the end, it's hard to say who was taking advantage of whom – and whether it really mattered that they were.

More than that, though, Oli Forsyth's script stands a sterling example of political theatre done right.  Forsyth wants to talk about homelessness, but there are no whiter-than-white heroes or black-hearted villains here; even criticism of the government is balanced by a brutal deconstruction of the liberal elite.  Some – but not all – of the characters take drugs; some – but not all – are both willing and happy to steal.  There are real moral conflicts built into the storyline, and Fosyth's script calls for genuine thought above tribalistic tub-thumping.

What's impressive too – and I'm trusting that Forsyth has done his research here – is that he lays out the web of bureaucracy which stands between homeless people and the help they need, finding ways to work this dry-seeming topic into a very human plot.  At one point, when the naïve young Hannah admits to breaking a Council rule, the reaction is as though she's just murdered someone.  And that's not the only time that Forsyth, without a hint of lecturing or condescension, takes it on himself to educate us.  If you've ever seen someone sleeping on the street and wondered why they don't just go to a shelter, there's a very good chance that Kings will fill you in.

All the cast deliver strong performances, and director Sam Carrack brings out the best in them with a driving, active dynamic.  Some of the most telling moments pass without a spoken word: look out for the silent toe-to-toe showdown between Caz and Bess, which passes so quietly the other characters don't even notice it but defines their relationship for the scenes to come.  As the young Hannah, Isaura Barbe-Browne charts a particularly delicate course.  At the start, her face regularly lights up with childish excitement and naïveté; by the end she's changed, scarily so.

Only once, when Caz almost literally climbs onto a soapbox, does the political dialogue tip over into outright polemic; it's a transformation which didn't quite carry me along.  There are a couple of lumps of exposition too – I can't believe that the defensive Bess would reveal her life story in as neat a package as she does – and director Carrack briefly forgets the first rule of performing in Fringe venues, that if you want your audience to see what's going on you'd better not do it on the floor.

But these small and oh-so-fixable glitches don't detract from a powerful and compelling play, which poses difficult questions about how both individuals and society behave.  It ends, fittingly, on a knife-edge; there are no easy answers to such a deep-rooted problem.  But it's an appeal, a challenge, and perhaps a warning, too.  Plenty to think about – and plenty to enjoy.