Wherever there are people, there are secrets. Even aboard a space slug crewed by itinerant nuns on a mercy mission. In the face of lies and betrayal, what is the truest service one can render to God?

Welcome to a future in which humanity has spread out across the stars, flying through the vast black on selectively-bred, heavily-modified slugs (go with it). The colonies rebelled against Earth’s rule and survived the atrocities Earth committed to try and end the war. Now Earth is tentatively reaching out in peace to re-establish links with her daughters, offering exotic trade and medicine in exchange for information. But it’s a subtle re-establishment of colonial rule: new colonies desperately need supplies, so Earth’s offer is too good to resist – but it comes with fine print.

The Church is also trying to re-establish control over its spacefaring itinerants, reinserting a hierarchy that the Sisters of the Order of Saint Rita have neither needed nor missed. They are used to the silent leadership of their Reverend Mother; they’re comfortable making their own decisions. They certainly don’t need an imperious man aboard to tell them what they may and may not do.

But everything is changing. Their ship is preparing to mate, sparking a religious controversy. A Sister has fallen in love and is considering leaving the Order. Another has no faith in God, although she loves serving Him. The secrets they hide from one another may shred their unity. And when a terrible disease begins to spread, the Sisters will need to stand together if they are to make a difference.

Oddly, the thing I found hardest to get my head around initially – even though I knew it was the premise going in – was the idea of spacefaring missionaries. I wanted more historical world-building to underpin this, but I realise that’s just my biases showing: the missions are alive and flourishing (hell, I’ve got a cousin-out-law who is/was a missionary), so why wouldn’t they branch out into space when the time comes?

Once I let go of my bias, I found so much to enjoy in Sisters of the Vast Black. For all its a tale of a religious order, it is more an exploration of conscience rather than of faith (which worked better for me, as I’m not remotely religious). It’s also one of those novellas that makes everything relevant without making developments feel forced, conflicts arising inevitably from the broader context and the secrets we learn about the crew. The characters take careful shape, defined by their secrets and their concerns. Their decisions carry increasing emotional weight as the crises they face escalate. And as with the best novellas, it didn’t feel rushed for all its brevity.

It’s fair to say that Sisters of the Vast Black – with its viral outbreak and central argument that taking action beats hopes and prayers (not to mention its subtext about mistrusting the ethics of those in authority) – has even sharper edges today than it did when I read it at the start of the year. But I’d strongly recommend it as a good read for now. While it is dark in places and has dystopian elements in its world-building, I found it an intensely hopeful read with its focus on doing the right thing (once you work out what the right thing is).

Expect a tale of faith challenged and sins confronted, with central themes of responsibility and community. And if you’re anything like me, expect to come out hoping for more stories of spacefaring nuns. This was my joint favourite novella of 2019 (with To Be Taught, If Fortunate) and while it works as a stand alone, the ending is wide open for future adventures I’d love to read.