A billionaire commissions a quantum physicist to create a time travel vest with advanced features, including voice activation, invisibility, force fields, and a molecular cutting device, with unlimited funding. The physicist successfully builds the single prototype, intending to deliver it to the billionaire who plans to use it for world domination. A mix-up causes the vest to be delivered to Maryann Lloyd, a librarian, instead of the billionaire, which was intentional as the physicist, a friend of Maryann's, did not want the billionaire to get it. The physicist is killed in an office fire set by the billionaire's men. Intrigued by the mysterious package, Maryann tries on the vest and, with detailed instructions, travels to her parents' wedding. After a safe return, she learns of the billionaire's anger and his pursuit of the vest. Maryann, however, has already begun her own series of adventures, using the vest's capabilities to intervene in historical events and help people, such as trying to rescue a woman during the Salem witch trials, confronting Al-Qaeda in Iran to help hostages escape, and attempting to warn people at the World Trade Center before 9/11. She travels to various times and places, meeting historical figures like George Washington at Valley Forge, Cleopatra and Mark Anthony and even Jesus, consistently using the vest to aid those in need and prevent impending disasters. The billionaire never succeeds in retrieving the time vest or capturing Maryann.