The Otherwhere Post

Three known worlds once existed side by side: Leyland, Barrow, and Inverly, connected by Written Doors at Blackcaster Station. Seven years before the story begins, a parasitic vine called the Aldervine, whose thorns send victims into an endless poisoned sleep, consumed the world of Inverly. The Written Doors were burned to prevent the vine from spreading, stranding thousands wherever they happened to be. Now, only couriers trained in scriptomancy, the art of enchanting existing handwriting, can cross between Leyland and Barrow to deliver letters. Eighteen-year-old Maeve Abenthy lives under the alias Isla Craig in Gloam, a city in Leyland, hiding her identity because her father, Jonathan Abenthy, was publicly blamed for unleashing the Aldervine. She carries a love letter her mother wrote to her father and plans to flee south.

One evening, a courier delivers an old letter addressed to "Maeve." The anonymous sender claims to be a childhood friend of her father's and insists Jonathan was innocent. Maeve abandons her escape plan and decides to investigate. She learns that postage records at the Otherwhere Post, the interworld courier service, might help identify the sender. She forges credentials, impersonates an applicant named Eilidh Hill, and infiltrates the Post's courier apprenticeship. The carriage driver who brings her to the Post turns out to be Tristan Byrne, the Postmaster's son.

At the Post, Maeve undergoes an arrival exam that includes a memory scribing, a written record that lets the reader experience someone else's memory. This one forces her to relive Inverly's final moments, including a stranger carrying her younger self to safety. The Postmaster, Onrich Byrne, assigns Tristan as Maeve's mentor. Tristan deduces she is not Eilidh because the real Eilidh's file identifies her as an equestrian expert. He confronts Maeve, who reveals her search for the letter's sender and proves her writing skill in Old Leylish, an ancient runic language. Tristan agrees to keep her secret.

Maeve investigates while attending classes. Steward Tallowmeade, one of the Post's senior instructors, mentions that a tracking office in Barrow could help identify the sender, but reaching Barrow requires the traveling scribing: writing one's full name on the wrist and speaking it aloud at the station wall. After seven years of hiding, Maeve cannot bring herself to write her own name. Meanwhile, a threatening letter written in rare red ink called Oxblood appears in her saddlebag. Someone at the Post knows who she is. Her roommate, Nan Ferro, an aspiring journalist, insists on befriending Maeve. Maeve learns that Tristan is disliked at the Post because his former apprentice, Cathriona Martin, died attempting a forbidden skin scribing, a scribing written directly on flesh.

After another dangerous Oxblood letter, Maeve forces herself to write her name and crosses into Barrow, where a specialist determines her anonymous letter was written on university paper and penned by a trained scriptomancer. On a return visit, Maeve and Shea Widden, Nan's mentor, discover that one of three bottles of Oxblood ink was purchased using the Post's archivist account. Nan helps Maeve explore Eldermoss Hall, her father's abandoned residence, where they discover he had a roommate scrubbed from all press coverage. Handwriting on the roommate's wall matches the anonymous letter. Maeve finds the roommate's name, Fion Claryman, in a library incident report and later spots it on a flyer for the Scriptomantic Exhibition in Barrow.

At the exhibition, Maeve infiltrates the opening reception and confronts Claryman, recognizing him as the stranger who carried her to safety from Inverly. Claryman explains he was eating lunch with Jonathan when the Aldervine appeared, proving her father could not have brought it. Jonathan ran to search for Maeve at her aunt's house while Claryman searched near the station; Claryman later found Jonathan with his throat slit. Claryman reveals Jonathan had developed a scribing called the Silver Scribing, which protects scriptomancers from the harmful effects of magic, recorded in a rose-covered journal, and gives Maeve a sealed paper he claims is a memory scribing.

Back in Leyland, Maeve reads the paper and discovers it is a form scribing designed to silence her. Ink floods her mouth and burrows beneath her fingernails, blackening her left hand. She swallows her supply of crematory ash, a white elm powder that repels scriptomantic magic, to neutralize the ink and flees into a snowstorm. Tristan finds her collapsed on a roadside the next morning, having ridden through the night on horseback, and brings her to Shea's grandfather's country house, where crematory ash saves her life.

Maeve reveals her true identity to Tristan, Nan, and Shea. Tristan produces the rose journal from his father's locked cupboard and reveals his own secret: He was pricked by the Aldervine in Inverly and has been kept alive by coffee scribings, skin scribings that prevent sleep. His father became Postmaster to protect Tristan from ministers who wanted to experiment on him, clearing the Postmaster as a suspect.

The group investigates Sibilla Creel, the head archivist, after Shea discovers that the love letter Maeve carries matches Sibilla's handwriting. They find Sibilla's name beside the Oxblood ink purchase in the accounting log and confirm she was in Inverly the day of the disaster. While Nan delivers Maeve's written account to the newspaper and Tristan prepares diversions, Maeve enters the Second Library to confront Sibilla.

Sibilla reveals she was Maeve's mother's best friend, fell in love with Jonathan after Maeve's mother died, and helped him research the Silver Scribing by providing restricted books. She insists she knew nothing about the murder. Before Maeve can press further, the real Aldervine, released from its glass case elsewhere in the library, wraps around Sibilla and pricks her. The vine never touches Maeve because crematory ash still coats her damaged left hand. In the lobby, she grabs the vine barehanded and hurls it away, but six puncture marks send her into the Aldervine's poisoned sleep.

Tristan wakes Maeve with coffee scribings written across her arm. Recovering, she pieces together that the Aldervine is a product of scriptomancy: It smells of scribing herbs, reacts to crematory ash, and leaves ink stains. She finds a cane with embedded glass from the smashed vine case and a bottle of Oxblood ink among the possessions of Steward Eamon Mordraig, the elderly steward of apprentices. Mordraig, believing drugged water will soon render Maeve unconscious, confesses. He unleashed the Aldervine to destroy the Written Doors, convinced that eliminating travel between worlds would make scriptomancy indispensable. He stole the Silver Scribing, murdered Jonathan, framed him, and later killed Cathriona and Claryman to protect his secret. He shoves Maeve from a window, but the coffee scribings in her system keep her alert enough to scream for help.

Maeve spends sixteen weeks recovering. Mordraig is arrested after the constabulary finds Claryman's body in his closet and a diary confirming the Aldervine's scriptomantic origin; a handwriting expert confirms Mordraig signed the archivist account for the Oxblood ink. Nan's article about Maeve runs in the Gloam Times. Tristan uses the rose journal to recreate the Silver Scribing on his own skin, and the Aldervine marks on his chest vanish. A statue of Jonathan Abenthy is erected beside Molly Blackcaster's ink fountain. The Postmaster makes Maeve a courier and invites her to join a new division alongside Tristan that will travel beyond the three known worlds to seek information for repairing the Written Doors. She slips the courier key into her pocket against her hip bone, in the place where her mother's love letter once rested.