The Bobbsey Twins at the Seashore finds the Bobbsey children and their parents on their way to a new summer adventure at the beach. We join the two sets of twins-Nan and Bert, age eight, and Freddie and Flossie, age four-on the train to Ocean Cliff. After a distressing ride with a wayward stage driver, the family arrives at the home of Aunt Emily and Uncle William, where the twins are happy to become reaquainted with their cousin Dorothy, a jolly and brave nine-year-old. The seashore provides many new pastimes-and dangers-for the children with new places to explore(and new opportunities to become lost), elaborate preparations for a boat carnival, high jinks with their new friends, and an affecting experience with Nellie McLaughlin, the lovely down-on-her-luck cash-girl first encountered in "The Bobbsey Twins in the Country."