There was a signal that if they were coming by land there would be one light and if they were coming by sea there would be two. Paul saw that they were coming by sea because there were two lights in the tower.
It is 1:00 A.M. and Paul is riding through Lexington. He is warning everyone that the British are coming over sea.
Paul rode through through towns telling everyone that the British were coming.
On Paul's way to Concord he ran into Dr. Prescot who was going to be a messenger also.
Before They got to Concord guards stopped them and told Paul that if he didn't answer his questions honestly he would blow his brains out.
Dr.Prescott snuck off and made it to Concord and warned everyone there.