When the site of the modern city of Mumbai first came under colonial rule in 1535, it was a marshy archipelago of low-lying islands. It was only after the British took control in the 1660s that the islands were built up and reclaimed in order to support a growing colonial population. Ghosh explains that the city was chosen for its proximity to deep harbors and its defensive capabilities as an island; however, these same features make it susceptible to extreme weather events like cyclones.

After Superstorm Sandy, Ghosh began to research the threat of extreme weather events in Mumbai, which rarely sees cyclones despite its location on the coast. He learned that geologists had discovered a previously unknown and active fault system off the coast of Oman—directly across the Arabian Sea from Mumbai. His collaboration with the atmospheric scientist Adam Sobel revealed several threats to the city of Mumbai, including a cloud of dust and pollution hanging over Indian waters that has dramatically changed wind patterns. Ghosh relates stories of a horrific Mumbai cyclone in 1882. Though the stories are ultimately revealed to be a hoax, he finds true descriptions of destructive storms from the 1600s through 2009. Ghosh warns that Mumbai, now a city of 20 million people, is under increasing threat as once-improbable storms brew in the Arabian Sea and the Bay of Bengal.