Haibara loses her phone strap of her favorite soccer player Higo on the train. Realizing the man who mistook her strap for his son's was most likely on his way to go digging for clams, Conan, Ayumi, Genta, Mitsuhiko, and Amuro go to the beach for the... (more) still not recovered Haibara in order to look for them. With Amuro's help, they learn the son's name. The Detective Boys successfully use the beach house's announcement system to find the son, but the man who's been watching Conan and his friends steals the strap as the father and son return it to them...