Would you explain more fully this Baptism of desire?

The Catholic Answers

Every human being has a conscience which dictates a natural law of moral obligation at least when he comes to the age of reason. If a pagan knows nothing of Christianity, and is ignorant of it through no fault of his own, he can at least repent of his personal sins against his conscience, and desire to do the right thing. God gives every man the grace to do this much. Now we know that a man should receive Baptism. If the pagan knew this he would receive Baptism. This sincere desire to do all that God would require implicitly includes the desire of Baptism, and God takes the will for the deed, granting sanctifying grace. Thus such a pagan would be saved. As is clear, anyone who has attained to the use of reason would be capable of this Baptism of desire.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty