Soon afterward, Tubman escaped again, this time without her brothers. She tried to send word of her plans beforehand to her mother. She sang a coded song to Mary, a trusted fellow slave, that was a farewell. "I'll meet you in the morning", she intoned, "I'm bound for the promised land. " While her exact route is unknown, Tubman made use of the network known as the Underground Railroad. This informal but well-organized system was composed of free and enslaved blacks, white abolitionists, and other activists. Most prominent among the latter in Maryland at the time were members of the Religious Society of Friends, often called Quakers. The Preston area near Poplar Neck contained a substantial Quaker community and was probably an important first stop during Tubman's escape. From there, she probably took a common route for fleeing slaves – northeast along the Choptank River, through Delaware and then north into Pennsylvania. A journey of nearly 90 miles (145 kilometers) by foot would have taken between five days and three weeks.