This is a historical novel following the true story of Mary Patten. She was the wife of Captain Joshua Patten, and travelled with him when he was hired to navigate the Neptune's Car, a clipper ship, from New York to San Francisco in 1856. The voyage was troubled from the outset. There was a plot of mutiny amongst the crew and Mary's husband fell ill as the ship reached the equator. She had no choice but to take command of the ship and navigate round Cape Horn while encountering exceptionally bad weather. Although Mary had learnt to navigate on a previous voyage with her husband, on the Neptune's Car she had to deal with an unstable crew and nurse her sick husband. She also discoverd that she was pregnant while on the voyage.