In September 1918, FDR became ill with pneumonia on his way home from an overseas trip. While unpacking his bags, Eleanor made a devastating discovery - a packet of letters from Lucy Mercer, her former social secretary.
It is unclear when FDR's relationship with Mercer began or precisely how involved she and Roosevelt were, but gossip about them had begun in 1917 and Eleanor may already have harbored suspicions that the letters served to confirm. According to some family members and friends, she offered Franklin a divorce. His mother threatened to disinherit him if he left his wife. His closest aide, Louis Howe, warned that a divorce would destroy his career. In the end, he vowed never to see Lucy Mercer again - a promise he did not keep.
The Roosevelts remained married, but thereafter were more political partners than husband and wife.