Supernova first presents itself as a road movie, which it certainly is. There are some gorgeous shots of the English countryside while a longtime couple—Sam (Colin Firth) and Tusker (Stanley Tucci)—visit places from their past. Tusker has surprises planned for this trip, which culminates in the first gig in a while for Sam, a well-known pianist.

We meet the two bickering about the value of GPS over maps. It is not quick, witty banter, though novelist Tusker is quick and witty. Within the first scene, which lasts maybe five minutes, we get a sense of their relationship, and like all long-term couples, it slips from sentimental to cutting and back in an instant. Already we get a feel of their history. Much of this is due to the casting. Firth as Sam is doing what Firth does best: stolid, emotionally controlled Englishman. Tucci, for his part, is the imp. Each creates a multifaceted portrayal and paints a realistic portrait of a committed 20-year relationship.

The signs that Tusker has early onset dementia are slowly revealed. There is no inkling of it until Sam returns to their RV at a road stop to find Tusker gone. He locates him about a half a mile away standing in the middle of the road looking confused. However, if we search back to earlier conversations—because most of us will be streaming this movie—the issue of his mental health is staring us in the face, and it’s the undercurrent of all their conversations.

What also makes Supernova work is the understated script and direction by Henry Macqueen. We are in very British territory here. Everything is quiet, understated, and occasionally unspoken. There is plenty of opportunity for fireworks, but Macqueen leans toward intimacy instead. There’s a lovely scene where Tusker and Sam discuss the future. They calmly, yet with urgency, plan for Tusker’s care, with Sam insisting he will be there till the end. Again, the dialogue ping pongs back and forth with a fluid emotionality. If this scene was played in the style of say Hillbilly Elegy, there would be a lot of Oscar-baity shouty histrionics. Instead, it’s a quiet conversation in the English countryside.

All decisions by Sam and Tusker stem from the latter’s diagnosis, but that is also a feint. The heartbeat of the film is the concept of devotion. These men are deeply in love and doing what they feel is best for each other, though what each wants may turn out to be slightly selfish. As the film meanders (in the best possible way) to its third act, this concept takes center stage, and this is where Firth and Tucci really dig in.

Essentially, the film is a classy showcase for two of our finest actors, and they deliver in spades. But it’s also a meditation on what it means to be a partner. Do we make decisions for ourselves or our significant other? When we think we are making a sacrifice, is it really for our benefit?

Though Supernova could have ended up a dour affair, it is decidedly not. It is sweet, sad, and surprisingly spry. A delight.