This is the first book in The Chronicles of St. Mary's series. The story is narrated by Madeleine "Max" Maxwell, a historian with a troubled past who discovers she belongs to a secret organization that travels through time.
Max's life changes twice. First, as a disruptive schoolgirl from a difficult home, her head teacher, Mrs. De Winter, offers to mentor her rather than expel her, launching Max toward a doctorate in history from the University of Thirsk. Ten years later, Mrs. De Winter recommends Max for a position at St. Mary's Institute of Historical Research, a sister campus to Thirsk.
During her interview, the Director, Dr. Bairstow, reveals St. Mary's true purpose: The institute investigates major historical events in contemporary time using small, stone-built vehicles called pods. The work is extremely dangerous because History itself functions as a living organism that will kill anyone who threatens to alter established events. Max also meets Chief Technical Officer Leon Farrell and Isabella "Izzie" Barclay, the unpopular IT head who becomes her lasting enemy.
Max enters training alongside six recruits and partners reluctantly with Sussman, a cocky trainee who pushes past her defenses. Training is grueling, covering academic exams, physical combat, and pod simulations. For her final test, Max is sent alone to what should be medieval Shrewsbury but is actually an empty plain with snow-capped mountains, a secret isolation test engineered by Farrell. The pod console goes dark, and Max endures 15 days alone before the system reactivates. Farrell tells her she is top of the class.
Max graduates into a critically understaffed History Department. Tragedy strikes immediately: Grant, a fellow trainee, is killed at the Peterloo Massacre of 1819 after running to save a woman and her children. One week later, Senior Historian Baverstock dies during an assignment to the Peasants' Revolt. The department shrinks to four: Max, Sussman, fellow historian Peterson, and Kalinda "Kal" Black.
On Max's first jump to 11th-century London with Peterson, a massive stone block crashes inches from them, illustrating History's lethal defense mechanisms. Their first major assignment sends Max, Sussman, and Kal to a World War I Casualty Clearing Centre in France. They endure harrowing conditions before fire engulfs the hospital. Max barely escapes and helps evacuate wounded soldiers, while Sussman retreats to the pod without assisting anyone. Farrell later identifies the fire as chemical sabotage.
During this period, Farrell gives Max a model Trojan Horse for her birthday, insisting she keep it safe. Their connection deepens during preparation for a three-month expedition to the Cretaceous Period, 67 million years ago. On a group outing, Farrell reveals he is from the future, sent back alongside Bairstow to protect the institute from those who want to exploit History for profit. Their chief enemy, Clive Ronan, a rogue former operative, blames Bairstow for his lover's death and has stolen two pods, killing the historians aboard. Farrell confesses his love for Max, and she reciprocates.
Max and Sussman depart for the Cretaceous in separate pods. For 74 successful days they document dinosaurs and gather data. On Day 74, Max wakes to find Sussman attempting to sexually assault her. She fights him off with pepper spray and locks her pod. Days later, Max is struck from behind and falls over a cliff edge, surviving by landing on a fallen tree. She finds Sussman's blood and severed boot, evidence of a raptor attack, and completes the mission alone.
Back at St. Mary's, footage reveals Sussman deliberately struck Max, working with Ronan's agents to kill her and weaken St. Mary's. When Sussman tried to escape, Ronan killed him. Max connects Sussman to the WWI hospital fire, realizing he arranged for her to be near the explosion. Farrell takes Max to a remote island to recover, and their relationship deepens. Max presents a dinosaur holographic film at St. Mary's and Thirsk to great acclaim, proposing the institute produce such films as a revenue stream.
When Max takes Farrell's senior technician, Dieter, on a return trip to the Cretaceous, they discover Ronan's commercial dinosaur-hunting camp. Bairstow organizes a combat mission to destroy it, deploying an electromagnetic pulse device, but the pulse accidentally unlocks the dinosaur cages, releasing predators. An explosion compounds the chaos. Barclay returns alone and declares Farrell, security chief Major Guthrie, Peterson, and security guard Markham dead. When Max demands a rescue, Barclay fires her and has her escorted off the premises.
Max descends into poverty in Rushford. She falls ill, learns she is pregnant at a clinic, and loses the baby within days. Mrs. De Winter finds her and takes her in, returning the Trojan Horse, which Mrs. Partridge, Bairstow's PA and Mrs. De Winter's sister, had saved. Max discovers a hidden compartment in the Horse containing the remote control for Farrell's personal pod. She programs a jump to 11 days after the disaster and departs alone.
In the Cretaceous, Max broadcasts her position with music and flares. She spots all four men alive but sees a T-rex on an intercept course. Max lures it away on foot, confronts it with pepper spray, and sprints for the pod under covering fire. All five crash through the door together.
Max delivers the men to Mrs. De Winter's house, where Bairstow waits. The men learn that no rescue was ever attempted and that Barclay has been running St. Mary's alone. Bairstow asks Max to return and deal with Barclay; she agrees.
Farrell learns about Max's miscarriage from Barclay and confronts her, questioning the baby's paternity. They later reconcile. Following Mrs. Partridge's repeated advice to do her laundry, Max finds a burned Cretaceous pinecone in her jacket lining, brought back inadvertently by Peterson. The cone survived the transition because it was nearly destroyed, having no future to alter. This breakthrough inspires a revolutionary proposal: St. Mary's can rescue lost historical treasures at the moment of their destruction. Max outlines three new sections: Pathfinders, timeline policing, and Search and Rescue. Bairstow approves, and the unit mobilizes.
The first rescue targets the Great Library at Alexandria in 391 AD. Teams retrieve an estimated 1,500 scrolls from the burning Serapeum, Alexandria's daughter library, and bury them in sealed jars for future discovery. That night, Ronan attacks with mercenaries, killing a researcher. When Farrell opens the door of TB2, the unit's large rescue pod, R&D head Professor Rapson and archivist Dr. Dowson emerge with a homemade flamethrower that ignites a dung stockpile, causing a methane explosion. Ronan escapes with TB2. Security officer Big Dave Murdoch is killed shielding Max, and Barclay, who arrived with Ronan's group, attacks Max before being struck down by Mrs. Partridge.
Injured in the aftermath, Max experiences a vision of Mrs. Partridge as Kleio, the Muse of History, and Mrs. De Winter as the Sibyl, a prophetic figure from ancient tradition. Kleio warns that History is under attack and directs Max to an anomaly "under the fourth step."
St. Mary's returns home to worldwide headlines as the scrolls' discovery is announced. Max connects Kleio's message to a cracked fourth step outside the front door. When workers repair it, they uncover a waterproofed box Bairstow buried 500 years earlier: a lost Shakespeare play and sonnets. The play contains a historical anomaly, depicting Elizabeth I executed while Mary, Queen of Scots survives. Bairstow tells Max that despite their triumphs, it is not over. The novel ends as a pause rather than a conclusion.