Determined to conquer a lifetime of shyness, Harriet Knight challenges herself to do one thing a day in December that scares her, including celebrating Christmas without her family. But when dog-walker Harriet meets her newest client, exuberant spaniel Madi, she adds an extra challenge to her list – dealing with Madi's temporary dog-sitter, gruff doctor Ethan Black, and their very unexpected chemistry. Ethan thought he was used to chaos, until he met Madi – how can one tiny dog cause such mayhem? To Ethan, the solution is simple – he will pay Harriet to share his New York apartment and provide 24-hour care. But there's nothing simple about how Harriet makes him feel. Ethan's kisses make Harriet shine brighter than the stars over moonlit Manhattan. But when his dog-sitting duties are over, and Harriet returns to her own home, will she dare to take the biggest challenge of all – letting Ethan know he has her heart for life, not just for Christmas?