Constellation Ending Explained: Bud and Henry Prove the Swap Can Be Undone

Warning: contains finale spoilers for Constellation.

Space messes you up. That’s the conclusion reached by former 1960s cosmonaut Irena Lysenko in Apple TV+ sci-fi Constellation. Irena knows space’s secret, which is that sometimes the astronauts that come back down from missions aren’t the same ones who went up there.

Every so often, spooky space physics pull a switcheroo and swap people from their own universe to a mirror versions with slight but unignorable differences such as the colour of the family car, to whether they’re alive or dead.

Before we get into Bud and Henry’s complicated finale business, a bit of context is needed:

The Mirror Universes

In Constellation, there are two mirrored universes plus a crossover space in which parts of both overlap, enabling people in Universe A to get the odd, destabilising glimpse of what’s going on in Universe B. Think Stranger Things’ the Upside Down, but with added physics.

The crossover area exists in space (because space is freaky) and on Earth in close proximity to the transportable Cold Atom Lab (the superposition experiment of which is responsible for a lot of this mess).

In Universe A, Irena Lysenko is the head of Russian space agency Roscosmos, and runs a facility that treats/hides away space travellers who, like Swedish astronaut Joanna Eriksson, have been switched from one universe to the mirror version and gone – for want of a better term – mad. In Universe B, Irena died in a space capsule fire in 1967 and her corpse was left to orbit the Earth as galactic litter.

Irena’s corpse, which now exists liminally in space in both Universes A and B (and who as “The Valya” – her childhood nickname – visits those affected by the mirror swaps as a kind of dream-ghost), collided with the International Space Station in October 2021, causing the death of NASA’s Paul Lancaster in Universe A, and of Jo Eriksson in Universe B. That collision, plus the superposition CAL experiment conducted by Paul in Universe A, caused Jo and Paul to swap from their original universes into mirror versions. Jo went from B to A, and Paul went from A to B. Neither are happy about it.

Constellation’s first season ended with Jo and Paul each trapped in the wrong universe, but they’re not the only ones…

Bud and Henry

“Whatever it is, it cannot be undone. You cannot change it ever. It’s done,” Irena told Jo about the swap. Jo finished the season having chosen to take the anti-psychotics prescribed to her and try to make her peace with the loss of her Universe B family and to get on with loving the Universe A family she had now. There’s no way back through the looking glass, assured Irena; Jo and Paul are permanently stuck on the wrong side of it.

Irena, though, is wrong. She knows that there is a way for these errant travellers to return to their rightful home, because it’s just been done by Bud Caldera.

In 1977, a depressurisation accident on fictional space mission Apollo 18 was resolved without casualties in Universe A, but caused the death of two astronauts in Universe B.

In Universe A, NASA’s Henry ‘Bud’ Caldera (known as Henry) came back to Earth a hero and went on to win a Nobel prize for physics, run the Jet Propulsion Lab and devise the CAL. In Universe B, Henry ‘Bud’ Caldera (known as Bud) came back to Earth disgraced and became a bitter alcoholic reduced to taking gigs talking about his NASA days on cruise ships.

Like Jo and Paul, Henry/Bud were switched from their universes to mirror versions, but unlike Jo and Paul, both versions of Henry/Bud remained alive, each in the wrong universe. Bud was originally from Universe A and stuck in Universe B (hence him getting details like the name of his childhood dog wrong in his memoir) and vice versa. That explains Henry’s coded talk to Irena of his “brother”, mirror conversations, and feeling another person walking alongside him since returning from space – it was Bud.

Jo and Paul Can Get Back, But…

In Constellation episode seven, Henry Caldera travels with the authorities to Joanna’s remote cabin to retrieve the CAL. While running towards the burning liminal cabin space, he begins to simultaneously perceive both Universe A, where he is physically in Sweden, and B, where his mirror self Bud is holding a gun to Paul Lancaster in an LA apartment. At the moment of shooting, presumably due to proximity to the CAL and the emergency situation (the other swaps also happened during dangerous accidents), Henry and Bud swap places.

Bud had been pushing into Henry’s universe, threatening to come for him in revenge for Henry having unwittingly taken his place in Universe A. He humiliated Henry by forcing him to urinate in front of a colleague, and his influence grew stronger to the point that – assisted by the CAL and the emergency – he made them swap places.

Now, Bud is back in Universe A where he started, and Henry has been transported back to Universe B, where he’s known as Bud and is a washed-up addict arrested for murder (pushing the author off the cruise ship) and attempted murder (shooting Paul Lancaster). Everything’s come up roses for Bud, who has escaped his terrible life and now gets to live the life Henry built as a wealthy Nobel prize-winning national hero.

Bud told Irena over dinner: “I’m not Henry. Henry is gone, and knock on wood, if I’m lucky, he’ll never be around again but he will remember who he was and he will live my old age, my addictions and my fucking failures.”

That’s why Bud smashed up the CAL with an axe and blamed Jo for doing it. He realised the CAL was functioning as a kind of portal-facilitator between the mirror universes, and he didn’t want Henry to have a route back. That also explains why Bud went to visit the Jack the Ripper tour guide in Universe A. Because in Universe B, that was the man Bud pushed off the cruise ship. He visited him, gave him flowers and instructed him to “live”, because he knew that in the mirror universe, he’d killed him.

Now, without a CAL in either universe (Bud Caldera never invented one in Universe B), there might seem to be no way back for Jo and Paul, but Paul happens to be the NASA scientist Bud trained to operate the CAL. If he can build another one, and a second season is announced, there is a possible route home, but (and this is a big but) because they, like Irena, are dead in their mirror universes, it would only lead them back to their corpses. All told, they’re better off staying put.

All episodes of Constellation are available to stream now on Apple TV+