The Dead Letter Delivery by C.J. Archer

The discovery of long-lost mail delivers a marriage proposal, a missing person, and a magical mystery.
A road trip with Gabe and her friends leads Sylvia to discover more about her mother's veiled past yet throws up several questions, too. The stack of unopened letters addressed to her family will hopefully provide answers. As she delves into the contents, a startling revelation emerges: the letters allude to a clandestine union between two magician families, hinting at the elusive identity of Sylvia's father.
Full of hope, she embarks on a quest to find the author of the letters, only to discover an artless youth who vanished decades ago, a dead man with the wrong name, and a hospital for former soldiers that connects them. The further Sylvia and Gabe delve into these mysteries, the more lies they expose, including long-buried secrets that certain individuals will stop at nothing to protect.
When danger strikes, Sylvia wonders if finding answers is worth the risk.