In 1894, a Syrian cotton merchant gave his Manchester house to God, on one condition: it could never be sold.

Manuscript conservator Layla Noor keeps its library of four hundred and eleven books alive from a sealed back room, holding the air at fifty-five per cent and checking it twice a day. If she stops watching, things fall. She has believed that since she was fourteen.

Landscape architect Zayd Mercer is the calmest man in Greater Manchester. He has been calm since his father died on a job three years ago, and he calls it patience. On his first day on site, he lifts the pin on Layla's shutter and lets the weather into her room.

What follows is a truce: half an hour every evening at five, two cups of mint tea and fourteen inches of stone between them on the ledge. Under the leaf mould, Zayd uncovers a salsabil, a carved stone chute built to slow water to the pace of a person walking. Inside the binding of a devotional manual, Layla finds the founder's deed, hidden there in 1909 by his widow, its margins full of her notes on the garden.

Then a developer offers £4.1 million for the site, and the board that runs the waqf votes to sell.

To save the house, Layla will have to let other people carry what she has always carried alone. And Zayd will have to open the door he shut the day his father died.

The Architecture of Tranquillity is a slow-burn, faith-forward love story about grief, patience and the difference between trusting God and giving up. It unfolds in a walled garden in Manchester, where the water runs beneath everything and nothing worth keeping is held up by one pair of hands.