On the final leg of the march, Dearborn was taken seriously ill with fever, forcing him to remain behind in a cottage on the Chaudière River. Later he rejoined the combined forces of Arnold and Gen. Richard Montgomery in time to take part in the assault on Quebec. Dearborn's journal is an important record for that campaign. During the march he and Aaron Burr became companions. Along with a number of other officers, Dearborn was captured on December 31, 1775, during the Battle of Quebec, and detained for a year. He was released on parole in May 1776, but he was not exchanged until March 1777.