Newton’s second law of thermodynamics – all systems tend toward entropy – governs the characters in Emily St. John Mandel’s debut novel. They tumble into one another’s orbits, toil over dead languages, and fret over their inert lives.

Mandel’s book is odd and fascinating: it’s a novel of ideas, with the shape and pace of a suspenseful mystery. On an October morning, Lilia Albert slips out of her lover’s apartment in Brooklyn and disappears. For her, it’s the continuation of a lifelong series of flights, which began as a little girl, when her father absconded with her and raised her as a fugitive, shuttling from one American town to the next, changing names and hair colours.

Lilia’s disappearance is crushing enough to dislodge her lover, Eli, from a life of miserable stasis spent writing a perpetually unfinished thesis and working a dull job at an art gallery. Eli follows Lilia to Montreal, lured there by the daughter of a private investigator who is obsessed with Lilia’s childhood disappearance.

Mandel tells an utterly absorbing story, pulling readers down the rabbit hole and keeping them racing through its long, strange warrens. The writing is vibrant, and Lilia is a vivid and haunting character.

At times, the book feels overstuffed. Mandel’s story occasionally veers off into meditations on Quebec language laws and a subplot dealing with life as a child of the circus. The story will pause for lyrical observation one moment, then conjure up washed-up cops in fedoras straight out of the pages of a thriller in the next. And the story is crowded with peripheral characters who have little to do with the central plot.

Despite these drawbacks, Last Night in Montreal is an exciting debut: a thriller, a love story, and a quiet ballad about life’s fleeting connections.