Within a minute, It's Not Yet Midnight has broken into a brawl. One man pushes another and, whoosh, the whole stage goes up: 20 bodies bashing each other around, throwing one another left and right, launching themselves full-throttle at some other poor sod. Bodies thump to the floor, elbows jut into stomachs, women pull each other's hair. Aggression is catching. It spreads like an airborne disease, and escalates into all-out attack. If it calms for a moment, the merest nudge sets it all off again: slaps and shoves and sh*t hitting the fan. It should be funny; so senseless it's absurd. It's not. Not with superpowers sizing one another up over Syria.

What follows sets itself against that start and offers another way entirely. Rather than butting heads, those 20 people come together as a team. They make human wedding cakes and pillars of people. They launch one another into the air and catch each other when they fall back to earth. Two people dance on the shoulders of a third. They balance head-to-head, whirl hand-in-hand and jive, joyfully, across a stage that was, not long ago, a battleground.

It's Not Yet Midnight is a testament to togetherness; a mark of what we can achieve when we work with one another. As with Sean Gandini's jugglers, it makes a virtue of simplicity – just bodies and space and a sprinkling of wit. Its performers become each other's apparatus. They form springboards and ramps. They're counterweights, safety nets and living trampolines. It's like a human assault course: people raising other people up.

That point extends into process. Based in France, Compagnie XY are a circus collective, and everything in It's Not Yet Midnight is created collaboratively; no artistic director, no outside eye. That's rare in circus, and for good reason: it's bloody hard. Doubly so with a company this size. Yet onstage they become a self-organising organism; individuals subsumed into a group, not showing off their own particular skills and strengths, but using them to support the whole. In that, It's Not Yet Midnight practices its preaching. It proves that it's possible.

Just behind each routine, you see the teamwork involved. This is circus that shows its supporting structures, as bodies form buttresses and build foundations. It's a show that says, quite literally, we're stronger together. Towers collapse into a heap as one, then rise back up, each person in sync. They have to be; physics demands it. At all times, everyone's got everyone else's back. They catch those that fall and step when things get shaky. If a move goes off-kilter, teeters on the brink, they seem to pause momentarily and check in: You ok? Are you?

It's enticing to watch – and not just for that spirit. As hour's go, this one's packed: flip after flip, feat after feat. Given there's no director, it's beautifully orchestrated. Small bursts of activity catch your eye and take it away from a set-up elsewhere. It's rambunctious, energetic and teeming with life.

At times, it seems to bounce off that title. This is circus attuned to the rhythms of the night, the way a mood can ripple through a crowd of its own accord. Like any late night, it's alive with possibilities. Mismatched couples come together across a dance floor and groups of friends fling themselves into flights of fancy. If that first brawl recalls chucking out (or kicking off) time, other sequences capture the wooziness of hot summer evenings or the giddiness of great nights out. Silly dances catch on. Stragglers spring onto shoulders. True, mood sometimes overpowers metaphor - and, at times, things trip into display team demonstration - but it mostly fits with its theme. No one controls the way a night goes. Group dynamics do what they will.

It's Not Yet Midnight runs at the Roundhouse until 23 April.