Coherence

The film commits to a literal interpretation of decoherence: macroscopic objects can in principle exist in superposition, and the comet provides the scenario in which this becomes locally true. The film does not soften the physics into metaphor.

Hugh's reading from his brother's physicist friend's book: the explanation of Schrödinger's cat as the working premise of the night.

The film operates inside a working many-worlds frame: every choice each character made has been realised in a parallel dinner party, and they are now able to walk between them. The film treats this as the explanation for the proliferation rather than as a metaphor for it.

The lottery-numbers method: each version of the party draws different numbers, allowing the characters to track which house they are currently in by means of a unique random tag.

A simulation reading is available and the characters articulate it themselves: each dinner party behaves like a sandbox instance whose state is consistent until a boundary crossing introduces inconsistency. The film does not endorse this reading over the quantum one, but it lets the characters consider it.

The houses-with-the-glowsticks tagging sequence: the protagonists treating their neighbourhood as an enumerable set of instances to be marked and tracked.

The film's third act forces a near-solipsist conclusion on its protagonist: if every version of you is real and accessible, the strongest argument for your version being the right one is your own attachment to it — and that turns out not to be enough.

Em's decision to swap herself into the "best" version of the dinner party — and the closing scene in which the displaced original-Em sees herself across the room.

The film is naturalist in temperament: no providence, no mysticism, no consolation. The comet is a physical event with physical consequences, and the moral chaos that follows is the expected behaviour of people inside a physics they did not anticipate.

The closing telephone call from the "other" Em — an ordinary call, with ordinary noise on the line, treating the multiverse as the new ground level of fact.