"The Outdoor Girls at Rainbow Lake" by Laura Lee Hope is a captivating tale of adventure and friendship centered around a group of four girls: Betty Nelson, Grace Ford, Mollie Billette, and Amy Stonington. The story begins with Betty receiving a mysterious letter from her Uncle Amos Marlin, a former sea captain, hinting at a grand surprise. This surprise turns out to be a motorboat named the Gem, gifted to Betty by her uncle. The girls are thrilled at the prospect of embarking on a cruise on Rainbow Lake and the surrounding river. The narrative unfolds with a series of events that test the girls' courage and camaraderie. Grace encounters a mishap when her horse, Prince, is spooked by a speeding automobile, leading to a fall that results in the loss of important papers. This incident also involves the injury of Mollie's younger sister, Dodo, adding a layer of emotional complexity to the story. Despite these challenges, the girls remain determined to make the most of their summer adventure. As they prepare for their cruise, the girls explore the features of the Gem, learning about its motor, galley, and sleeping arrangements. Captain Marlin, with his nautical wisdom and jovial personality, guides them through the intricacies of boating, ensuring they are well-prepared for their journey. The story highlights themes of resilience, friendship, and the excitement of exploring new horizons.