A picture-book account of the annual spawning of horseshoe crabs on the beaches of Delaware Bay also touches on the ecosystems surrounding the spawning, the professional and citizen science involved in tagging the crabs and counting accompanying birds, and the natural history and origins of the horseshoe crab. All of this takes place in a two-tiered narrative: a bold, larger font offering a simple action statement (e.g., “It’s starting.” “They’re arriving.” “They’re tagging.”), and a still-brief but more informative, graceful explanation of that action associated with each statement (e.g., “Scientists and vacationers brush sand off their binoculars. They pack up data sheets, beach chairs and stories …”). Detailed yet impressionistic watercolor illustrations provide an alluring backdrop for an inviting, informative look at fascinating creatures. End matter includes far more detailed information about horseshoe crabs. (Ages 5–9)