Murder can be so old hat.

Cousins Scarlett Parker and Vivian Tremont's fashionable London hat shop, Mim's Whims, is visited by a new customer bearing an old hat box. Ariana Jackson is getting married and wants to restore her mother's bridal hat and veil for the occasion. The elegant item was made by Scarlett and Vivian's grandmother over thirty years ago, so they are delighted to take the job.

When Scarlett goes to Ariana's office to consult about the restoration cost, she finds her outside, standing over her boss's dead body. Though Ariana claims to know nothing about his demise, the investigation unveils a motive for murder. Now, with the bride-to-be in custody and the wedding on hold, Scarlett and Viv must find the real killer before Ariana's future is boxed up for good.