Nat works at a store that allows people to access prisms—a device that uses quantum mechanics concepts to create and access alternate timelines and realities. The machines have their limitations, with each one tied to a specific quantum event that the machine itself induces when first activated and provides access to an alternate reality from that point forward. Communication between the timelines is finite, however, since each prism only has a limited capacity for text messages, audio calls, or video chats before its ability to connect to the alternate timeline runs out. When one activates a prism, one's alternate self also activates a prism in their respective timeline, essentially allowing communication between parallel versions of oneself who up until that point, have led identical lives. The prisms accumulate value as time goes on and random events or different choices cause the two timelines to diverge, giving greater insight to people from one timeline into the different potential outcomes of their lives. Dana is a psychologist who runs a support group for people who have become obsessed with prisms and the paths their alternate selves have taken. She also bears her own regret and guilt surrounding an incident as a teenager during a school trip where, in a split second decision after being caught by teachers, lied that the drugs in the hotel room she and her best friend shared belonged to her best friend (the drugs belonged to both of them). Dana feels this incident set her best friend, Vinessa, off on a bad path in life, making her feel she is in perpetual debt to Vinessa.
Nat works with Morrow at SelfTalk where customers pay to use the store's prisms to talk to their parallel selves. Although SelfTalk was popular when only corporations could afford prisms, the ability for individuals to purchase their own prism has diminished their customer base. Morrow, the manager of the shop, runs scams to make more money and involves Nat in a plan to con a member of Dana's support group into selling his prism for its valuable information. Morrow's plan involves a celebrity couple who suffered a fatal car crash with only one of them, Rick, surviving the crash. Lyle, Morrow's target, has the prism that accesses the timeline where Rick's husband is the survivor. The plan involves convincing Lyle to sell his prism and coordinate with parallel universe Morrow to convince the survivor in their respective universe to buy the prisms at a high price in order to speak with their deceased partner from another timeline. In the meantime, Morrow pulls off another scam where he cons an old lady into bonding with her parallel world self and depositing her money into a fraud fund under the guise that it will be received by her parallel world self after she passes away. Unbeknownst to her, transferring money to a parallel universe is impossible. Her son visits the shop, demanding the money be returned and ends up shooting Morrow in the face when Morrow refuses. Morrow's death leaves Nat to handle the deal on her own and she begins to question her motive for carrying out the scam. She opens up in one of Dana's support group sessions about Morrow's death and questions the point of choosing to do the right thing if in an alternate universe, her alternate self would have chosen to do otherwise. Dana tells Nat that when one chooses to make the right decision, it's more likely that that all of an individual's paraselves would have chosen the same instead of diverging again. Nat remembers this on her visit to sell her prism to the grieving celebrity and chooses not to accept payment for her task. Nat overhears Vinessa asking Dana for money to pay tuition for school. She grabs a drink with Vinessa and hears her side of the story in which Vinessa blames Dana for losing the chance to have a successful, happy life. Nat realizes Vinessa has only been using Dana as a scapegoat for all her problems. Vinessa may blame Dana for what she did fifteen years ago but over time, the outcome of her life is ultimately Vinessa's responsibility. In a rare act of selflessness, Nat obtains multiple prisms from several different timelines in which alternate versions of Dana each give a different account on the drug incident. In one timeline, Dana claims the drugs are hers. In another, Dana says they both took responsibility for the drugs. However, no matter how the incident was handled, the outcome was the same: Vinessa's life ultimately spirals downhill and she ends up blaming Dana. Dana learns that irregardless of what choice she made, Vinessa would have been angry with Dana in pretty much any scenario Dana could have selected and everything would end up the same. Dana realizes that she is not responsible for the way Vinessa has chosen to live her life and is relieved from the guilt she has carried for so long.