Christian faced the temptation to veer away from the path that he had originally set out upon. He met Mr. Worldly Wiseman along the way, who convinced him that he should leave the path and go visit Legality, telling him that this was the easiest way to salvation. Of course, this represents the idea that man can get to Heaven by doing works, rather than through faith alone.
Fortunately for Christian, he met up again with Evangelist, who reminded him that there is only one way to Heaven - the Wicket Gate, which is the narrow path that all men must stick to if they want to gain salvation. All the good works in the world (Legality) will not save one's soul.
The link below will take you to the eNotes summary of this book. Good luck!