The Marigold by Andrew F Sullivan

In a near-future Toronto buffeted by environmental chaos and unfettered development, an unsettling new lifeform begins to grow beneath the surface, feeding off the past.

The Marigold, a gleaming Toronto condo tower, sits a half-empty promise: a stack of scuffed rental suites and undelivered amenities that crumbles around its residents as a mysterious sludge spreads slowly through it. Public health inspector Cathy Jin investigates this toxic mold as it infests the city's infrastructure, rotting it from within, while Sam "Soda" Dalipagic stumbles onto a dangerous cache of data while cruising the streets in his Camry, waiting for his next rideshare alert. On the outskirts of downtown, 13-year-old Henrietta Brakes chases a friend deep underground after he's snatched into a sinkhole by a creature from below.

All the while, construction of the city's newest luxury tower, Marigold II, has stalled. Stanley Marigold, the struggling son of the legendary developer behind this project, decides he must tap into a hidden reserve of old power to make his dream a reality — one with a human cost.

Weaving together disparate storylines and tapping into the realms of body horror, urban dystopia, and ecofiction, The Marigold explores the precarity of community and the fragile designs that bind us together.