An alien arrives on Earth in human form, lands naked on a Cambridge road, and is struck by a car.

Police apprehend the naked alien on the Corpus Christi college campus and take him into custody.

After a psychiatric evaluation, the alien is institutionalized in a mental hospital and sedated with diazepam.

Andrew sneaks to his university office and deletes the Riemann hypothesis proof titled "Zeta" from the computer.

Andrew discovers an email to Daniel Russell containing the proof and deletes both the message and the attachment.

Andrew visits Professor Daniel Russell at his home and secretly induces a fatal heart attack.

Daniel Russell dies in Tabitha's arms while Andrew watches, unexpectedly overwhelmed by grief.

Andrew heals the family dog Newton's blindness and discovers the emotional power of music for the first time.

Andrew follows Gulliver on a walk and watches him stand dangerously close to an oncoming train.

When Andrew nearly reveals his alien identity to Ari, his home planet attacks him with blinding violet pain.

Andrew catches a drugged Gulliver falling from the roof during a suicide attempt, shattering his own legs.

Andrew demands his home planet strip him of his alien powers so he can become fully human.

Andrew casually tells Isobel he slept with student Maggie; Isobel demands a divorce and orders him out.

Andrew kills the home planet's replacement agent Jonathan to stop him from murdering Gulliver.

Andrew reunites with Newton and Gulliver on a Cambridge bench and decides to return home to Isobel.

An alien from an advanced civilization arrives on Earth disguised as Cambridge professor Andrew Martin, tasked with erasing all proof that humanity has solved the Riemann hypothesis. He eliminates the key witness Daniel Russell but finds himself increasingly drawn to the family he is supposed to destroy. His growing love for Isobel and Gulliver overpowers his mission, and he chooses to surrender his alien powers and become fully human. When his home planet sends a replacement agent to finish the job, Andrew commits what his species considers the ultimate crime to protect the son he loves. Cast out of his adopted family and living in exile, Andrew spends a year pining for Isobel before resolving to return and reclaim the love he sacrificed everything to find.

The core mission and transformation of an alien living as Andrew Martin.

The alien escapes an ambulance by ripping off medical equipment and fleeing into the Cambridge night.

The alien enters a Texaco gas station and uses a Cosmopolitan magazine to learn the English language.

The alien steals math books written by Andrew Martin from a Cambridge bookstore while evading police.

Andrew meets a philosophy-loving patient named Zoë in the mental hospital dining hall.

Andrew convinces the hospital psychiatrist to discharge him by presenting a calm, measured account of his situation.

Andrew sneaks out of the Martin home against Isobel's instructions to reach his university office.

Gulliver reluctantly confirms he was told about the Riemann hypothesis solution the night before Andrew disappeared.

Andrew finds a book of American poetry on the Martin shelves and is moved by its beauty and imagery.

Andrew helps Isobel load the dishwasher for the first time, shocking her with his uncharacteristic domesticity.

Andrew calls the Martin family's mother and learns the household has been fractured for at least a year.

Andrew attends Daniel Russell's funeral alongside Isobel and watches Tabitha's grief deepen into fragile widowhood.

Andrew hacks the Facebook profiles of Gulliver's school bullies, replacing their names with shaming messages.

Gulliver fights and defeats his bully Theo Clarke in a confrontation outside, after Andrew coaches him.

Student Maggie takes Andrew to the Hat and Feathers pub and describes human life as building a toy castle.

Andrew writes a 97-point guide called "Advice for a Human" for Gulliver before leaving the family home.

These events capture the texture of Andrew's bewildered adjustment to human life, from his comically chaotic first hours on Earth to the everyday domestic scenes that gradually soften him. Through encounters with a philosophy-loving hospital patient, stolen poetry books, and the revelation of an inherited affair, Andrew builds a portrait of the fractured Martin family he has stepped into. Secondary characters like Zoë and Maggie illuminate human paradoxes that Andrew struggles to reconcile with his alien logic. Acts of protection and revenge — hacking bullies online, coaching Gulliver through a fight — reveal Andrew embracing a fatherly role he was never supposed to play. The pool closes with Andrew's most lasting human gesture: a heartfelt written guide on how to survive being alive.

The smaller moments that quietly shaped Andrew's human transformation.

Andrew chooses to remain voluntarily in the mental hospital rather than escape, deciding to study humans from inside.

Isobel visits Andrew in the mental hospital, and he feels an unexpected and inexplicable pull toward her.

Andrew discovers crunchy peanut butter and realizes, for the first time, he is capable of experiencing genuine pleasure.

Andrew contacts his home planet after killing Daniel Russell and argues for sparing Isobel and Gulliver.

Andrew uses mind control on a sleeping Gulliver intending to kill him, but Gulliver wakes and violently attacks.

Andrew argues to his home planet that humans uniquely exist in both conscious and subconscious worlds simultaneously.

Andrew finds Isobel's hidden unpublished manuscript and discovers the depth of her private unhappiness and buried dreams.

At the football match, Ari reveals the long-held secret is about Andrew's student affair, not the Riemann hypothesis.

Andrew secretly uses his alien powers to restore Isobel's broken lightbulb; they share a warm, spontaneous embrace.

Andrew's alien hosts take over his body in bed to kill Isobel; he fights them off and they make love.

Andrew wakes in a hospital after being beaten unconscious in a street fight, with Isobel beside him declaring love.

Andrew returns home to find the replacement alien Jonathan waiting and learns that Jonathan killed Ari.

Isobel witnesses Jonathan's alien body disintegrating in the backyard and retreats into trauma, rejecting Andrew entirely.

Andrew settles in California, drinking heavily and travelling widely, unable to stop pining for Isobel and Gulliver.

Andrew spots Isobel giving money to a homeless man in Cambridge and resolves to seek her forgiveness.

This pool follows the pivotal thresholds where Andrew's alien logic cracks open to reveal something unmistakably human underneath. From his first deliberate choice to stay in the hospital and study humans, to the taste of peanut butter that proves he can feel pleasure, each event marks a point of no return. His love for Isobel deepens through secret kindnesses and hard-won vulnerability, while his home planet grows increasingly violent in its efforts to drag him back. The arrival of the replacement alien Jonathan forces Andrew to commit what he considers the ultimate crime against his own kind, costing him his adopted family. After a year of solitary exile and self-medication in California, his final glimpse of Isobel in Cambridge crystallises the resolve to risk everything on the possibility of her forgiveness.

The key decisions, discoveries, and emotional shifts that made Andrew irreversibly human.