The following version of this book was used to create the guide: MacInnes, Martin. In Ascension. Atlantic Books, 2023.

MacInnes’ novel is divided into five sections with an afterward which correspond to the different stages of discovery in the life of its scientist first-person narrator Leigh. Part 1, Endeavour, opens in Rotterdam, Netherlands, where Leigh grows up on land that must be continually engineered so that the ocean does not reclaim it. Leigh’s father works as a water engineer and her mother is a mathematician. Her father is violent with his two daughters, Leigh and her younger sister Helena, but Leigh suffers the brunt of his beatings. She escapes through nature, which she recognizes from an early as healing.

Leigh’s father dies and she becomes a marine biologist, traveling to the Azores Islands to study microorganisms in mountain lakes and then eventually joining the crew of a ship named Endeavour headed for a newly-discovered hydrothermal vent deep in the Atlantic Ocean. Leigh meets her mentor Amy, an engineer, aboard the ship and becomes the first crew member to volunteer to dive in the ocean above the vent. She experiences an alternate state of consciousness and the pull of an alien consciousness while diving. The crew discovers the trench is deeper than any other in the world and is shaped like a Cassini oval. Leigh shares her ideas about algae with Amy and other scientists on board.

In Part 2, “Datura,” Amy recommends Leigh for a job at China Lake Station at the Institute for Coordinated Research, where she is promised unlimited funding and where everything is kept secret. Leigh meets Uria, the projects manager at the Institute, who becomes another mentor. At first, she does not know the details of the space mission the Institute is planning, but over time, and after having success in growing algae for consumption in space, she learns her agricultural system will be aboard a spaceship bound for the outer solar system. The scientists believe they have been contacted by an alien consciousness because satellites have picked up an image of a giant red oval with carvings floating in space. They name the object Datura, after a plant that grows in the Mojave desert near China Lake. Leigh learns the scientists have picked up a signal from Voyager 1, NASA’s longest running spaceship, but that is has flown way past where they expected it to be. They believe alien life has contacted Voyager and carried it or assisted it. Leigh learns the objectives of the mission are to contact Voyager as well as develop technology for mining off-world. Leigh learns the scientists will use the newly-discovered propulsion technology, which they believe might have come from aliens, for the mission. Secrecy is tight at China Lake and the nefarious influence of big business and profits from mining in space looms in the background of Leigh’s research.

To help with her research and because she has few family ties, Uria recommends Leigh train to become an astronaut on the mission to the Oort Cloud, the furthest reaches of the solar system. She begins training and meets her fellow astronauts: K or Karius and Tyler. In Part 3, “Kourou,” the astronauts are whisked away early in the morning to a secret spaceport in French Guiana called Kourou. There they continue to prepare for the mission and await the launch.

In Part 4, Nereus, Leigh and her crew mates fly into space aboard Nereus, an oval-shaped spacecraft with an algae garden inside, designed by Leigh. The propulsion system is strapped to the outside of the craft, and operates autonomously. Although scientists tested it on earth, they never gained full understanding of how it works or its effects. The astronauts successfully endure several accelerations or jumps aboard Nereus, but their senses begin to change and they develop disassociation with their bodies in zero gravity. Tyler, the captain, cuts himself while doing routine maintenance, and loses a great deal of blood. Leigh saves his life by cauterizing the wound with small antennae and a microwave device. The algae grows exponentially as the crew sails farther and father into the solar system. When they reach the Oort Cloud, something strikes Nereus and everything goes dark. They loose communication with earth. It seems as though they might die on the mission.

Part 5, “Ascension,” switches to a third-person narrative stance as Leigh’s sister, Helena, searches for her remains and information about what happened during the mission. Helena has had to take responsibility for their mother and her death, and then Leigh’s death, although the Institute provided very little information. Helena travels to Ascension Island with Maria, Uria’s daughter, where they find the log cabin that Leigh and her two crew mates were supposed to spend their post-mission quarantine. This gives her some closure. Meanwhile, the Institute has broken up into subsidiary companies, one of which mines asteroids off-world, although many of their employees die on the missions.

The afterward, “Oceana,” jumps back to Leigh’s perspective as she re-enters earth’s atmosphere in a capsule. Landing in the ocean, she sees that Karius and Tyler did not make it, but her algae crop surrounds her.