A group of retired history and geography professors at the University of Hawaii discover an ancient maritime navigational device, a spherical astrolabe, in a trunk in the attic of a dilapidated mansion one of them is renovating. Accompanying the astrolabe is a 500-year-old memoir that includes detailed instructions for turning the astrolabe into a time machine. The group follows the instructions and ends up in 15th century Mogadishu, Somalia. Things go wrong very quickly, and they have to return to their own time. All of them except one—Professor Horacio Fuente.