The Island of the Day Before () is a 1994 historical fiction novel by Umberto Eco set in the 17th century during the historical search for the secret of longitude. The central character is Roberto della Griva, an Italian nobleman stranded on a deserted ship in the Pacific Ocean, and his slowly decaying mental state, in a backdrop of Baroque-era science, metaphysics, and cosmology. Plot summary Roberto della Griva, a 17th-century Italian nobleman, is the sole survivor of a shipwreck during a fierce storm. He finds himself washed up on an abandoned ship, the Daphne, anchored off a mysterious Pacific island through which, he convinces himself, runs the International Date Line (roughly 180° longitude). The ship is fully provisioned, he discovers, but the crew is missing. Although the shore is very close, Roberto is unable to swim, and is therefore stranded on the ship. With no way of locating himself or finding a way home, Roberto abandons himself to philosophical contemplation, roaming the crewless ship and composing letters to his beloved Lilia, a lady he met in Paris some time prior to his misadventure on the high seas. Roberto soon discovers he is not alone on the ship. Someone else is stealing eggs from the hens, rummaging through the letters he writes to Lilia: in short, there is an Intruder aboard. Finally Roberto finds out the intruder: an old German Jesuit called Gaspar Wanderdrossel. Wanderdrossel relates to him the mission of the Daphne's crew and the crew's sad ending at the hands of the natives. Gaspar explains to Roberto that his mission was to discover how to measure longitude by charting the eclipses of the moons of Jupiter. He also educates Roberto to other recondite astronomical means being used to seek this measure. The priest comes to take on a mentor role with Roberto. He urges Roberto to learn to swim. Roberto tries and tries again, but fails. Gaspar finds his own way to reach the Island,and Roberto is left alone again. He begins to reminisce about his life and his love. He becomes obsessed about his allegedly evil twin brother, who is split from his own persona through a process reminiscent of the doppelgänger effect, and thus accusing him of all the bad things that happened in his life. The brother takes blame mainly for his bad choices and is present to sweeten the disappointments of life. Through this