Throughout the various chapters, Cloud Atlas describes how many characters across time and space have a birthmark in the shape of a comet. Robert Frobisher, Luisa Rey, Timothy Cavendish, Sonmi~451, and Meronym all share this birthmark. Occasionally, they realize that they’re not alone in having this birthmark. Cavendish, for example, mentions the similarity between his own birthmark and one described in Half-Lives, while Luisa notes the similarity between her own comet birthmark and one mentioned by Frobisher in his letters to Rufus Sixsmith. The comet birthmark is a sign of unity across the ages. Even though the characters are very different people, they have inherited some form of connection that the mark on their skin symbolizes. The birthmark is a natural occurrence, something the characters are born with. The natural mark on their skin unites the characters by birth, as each one inherits something of the others from the past. Rey listens to Frobisher’s sextet, for example, while Cavendish becomes emotionally invested in Luisa’s life story. The last thing Sonmi does before her arrest is watch the film about Cavendish’s escape from the retirement home, while Meronym’s people know and share recordings of Sonmi’s manifesto.