Sam, Abby and their new friend, Mai, find themselves time traveling to 1878 where they witness the filming of the first moving picture by Eaduard Muybridge at Leland Stanford's Palo Alto horse farm. The adventure changes pace when they catch a cable car ride to the magnificent mansions of San Franciso's Nob Hill. Their journey takes a dangerous twist, however, when Mai, who has the key to their being able to return to the present, is captured in Chinatown. This is book 4 of the Secret Santa middle-grade mystery series.