“Dual” takes place seemingly at the present time, but with one technological advancement: cloning yourself is not just a possibility but a reality. The glossy advertisements for the “replacement” process proclaim it as a loving thing to do: if you are going to die young, there will still be a “you” around, ready to take your place. Your loved ones won’t need to grieve. The “replacements,” as they are called, are generated from just a drop of spit, and they spend time with the “original” during the period of transition, getting familiar with the original’s life, all the likes and dislikes, in preparation for the eventual takeover. The transition from original to replacement is supposed to be seamless.
But things don’t play out that way with Sarah (Karen Gillan), suffering from a mysterious terminal illness. Sarah has a boyfriend named Peter (Beulah Koale), and a perpetually disapproving mother (Maija Paunio), the only two people who really “count” in her life. Sarah keeps her illness secret from both of them, and makes the decision to create a “replacement.” Financial worries are brushed off by the sales rep: after Sarah’s death, the “replacement” will be stuck with the bill. When the replacement strolls into the room, it’s a perfect match except for one thing. The replacement has blue eyes whereas Sarah’s eyes are brown. No problem, the replacement can wear colored contacts!
But the anomaly is a sign of things to come. Very quickly, Sarah’s replacement shows signs of unnerving ambition. She’s not just trying to replicate Sarah. She’s setting herself up as better, in every way. She stares at a framed photograph of Sarah and Peter, and turns it face-down. She makes comments about Sarah’s clothes not fitting her: she is a smaller size. She is better in bed, more adventurous. Sarah’s mother prefers replacement Sarah to the real Sarah. So does Peter. Sarah finds herself squeezed out of her own life.