Maeve Bennett has spent years making herself indispensable-to her family, her work, and the people she loves-only to discover that being needed is not the same as being chosen. Julian Hart is an architect who designs spaces meant to last while keeping his own heart carefully out of reach.

When their dates abandon them at a mutual friend's Sunday wedding, Maeve and Julian find unexpected comfort in each other. A shared dance leads to breakfast the following week and, soon, an experiment inspired by Maeve's late mother: Give anything one hundred Sundays, and you'll know whether it's meant to stay.

To keep things simple, they establish five rules-including no interfering in each other's relationships and, most importantly, no falling in love.

What begins as a simple arrangement slowly becomes the most dependable part of their lives. Through changing coffee orders, private jokes, shared grief, and dreams neither has dared to pursue, Maeve and Julian create an intimacy that becomes harder to explain-and even harder to lose.

As Sunday one hundred draws closer, they must confront the question their rules were designed to prevent: What if the person you promised not to love is the one who has been choosing you all along?