On the evening of May 12th, the Planter docked at Charleston. Captain Relyea and the other white officers left the ship to visit their homes. Gen. Ripley was attending a party in Charleston, leaving Smalls in charge of the ship. Smalls made no move until 3:00 a.m. Then he hoisted the Confederate flag and sailed out into the harbor, observing every protocol as it would have been carried out under Relyea's command. The ship made one quick stop to take aboard the five women and three children who were huddled in their small boat and then sailed straight for Fort Sumter.
To further the subterfuge, Smalls put on the captain's braided jacket and trademark straw hat, taking on the captain's jaunty stance on the deck and hoping that the shadows of early dawn would hide the difference in pigmentation. As they passed Fort Sumter, he gave the secret countersign by blowing the whistle in a pre-arranged code. It worked. Waved on by the Officer of the Day, the Planter sailed out into the harbor mouth. Then it made a quick turn, hoisted a white flag of truce, and headed straight for the nearest ship in the Union fleet that had been blockading the southern coast ever since November.
When officers of the U. S. Onward boarded the smaller ship, Smalls saluted and announced proudly, "I have the honor, sir, to present the Planter, formerly the flagship of General Ripley . . . I thought these guns might be of some service to Uncle Abe."
He delivered to the Yankees the four cannons that were aboard the Planter, but his more important contribution was his knowledge of what the Confederate forces were planning. He knew that the Confederate Marion Rifles and the Eutaw Battalion had joined the effort to evacuate Cole's Island. They had constructed footbridges across the Stono River as an avenue of escape in case the road was cut off along the Stono to Battery Island. Then, to "keep up appearances," they had placed dummy cannon where they had removed the real ones. The flag still flew and the men simulated complete military occupation although there were only about thirty soldiers there. All buildings were prepared for destruction by burning when fired upon by the federal fleet. That news meant that the way was open for Union troops to move onto James Island via the Stono River in preparation for the taking of Charleston itself.