Being a new stepbrother to little Luisa isn't always as much fun as Javier first thought it would be. When Luisa falls off the bridge leading to Javier's fort, his mother tells him they'll have to take the bridge down.

After some careful thinking, Javi realizes that he might be able to convince his parents to let him keep the bridge to his fort if he can design a safer one. With some help from his cousins and some inspiration from his little sister, Javi comes up with a new bridge design. But will it pass the inspection of his stepfather Joe, a real civil engineer?

Readers are invited to create beam, arch, and suspension bridges. With some creativity and knowledge of the engineering design process, everyone can engineer!