Rob, Carl, and Carl’s sister Helen have a green duckboat that they take out every morning, spending the first few hours swimming and the rest of the day traipsing about the island shooting crows and spotting herons. This routine is broken when Richard Wellman comes in with a motorboat and offers them a ride; Rob refuses, but Helen takes him up on his offer. As the days pass, Helen begins to spend more and more time with Richard – she talks about him all the time, and barely spends any time with the other boys. Rob and Carl go by themselves to the island and Rob, in a fit of suppressed jealousy, shoots a rain-crow. Carl warns him that killing a rain-crow brings bad luck, but Rob shrugs off the warning until they get home, and he sees that Helen is more besotted with Richard than ever. In a moment of doubt, Rob returns alone to the island and buries the rain-crow. Richard comes by with his boat and another vessel, and they offer to race. Both Richard and Rob are determined to let Helen win, while they fight for second place – Rob secures the victory, but Helen remains unimpressed. Carl observes a few days later that the river level has lowered, and on a night with bad weather, Richard comes by and offers to take Helen on a ride. Both Rob and Carl warn her against it, but she is adamant and accuses Rob of being jealous. They go out together, but in the poor conditions, the sandbar is impossible to spot; Richard crashes the boat and Helen is flung into the water. Carl and Rob row out to save them, and Helen frantically rows back with the green duckboat to pull in the wreckage. They use the oars as leverage, hoping that it stays. Come morning, however, Carl finds that the lovely green duckboat has sailed away.