Adam of the Road showcases a delightful array of medieval characters, each representing different occupations from minstrel to pilgrim, preacher to miller, and merchant to plowman. The protagonist, Adam Quartermayne, is an eleven-year-old boy at the start of the story. He attends a monastery school while his minstrel father travels to France in search of new ballads. Adam, who is described as having tousled hair, a snub nose, a wide mouth, and a square jaw, eagerly anticipates his father's return. His curiosity about the world adds a sense of freshness and excitement to the story as it unfolds from his perspective.

Adam is a typical boy in many respects. He becomes so absorbed in a miracle play that he loses his balance and falls off a wall, resulting in a concussion. He deeply admires his father and loves his dog, Nick. When Nick goes missing, Adam bravely sets out to find him, even swimming across a river to pursue the man who stole the dog. Throughout the book, Adam's understanding of people becomes more acute, yet he remains optimistic. He learns that most people are fundamentally kind and good.

Roger Quartermayne, Adam's father, is an exceptional minstrel. His vast knowledge of French romances and Arthurian legends makes him a welcome guest at manor houses, where he entertains and receives lavish gifts, including a war horse. Although he is caring, Roger is often absent due to his dedication to his craft. His major flaw is a penchant for gambling, a vice that has led many minstrels to ruin.

Supporting characters that enhance the plot and themes include Adam's schoolmate Perkin and the minstrel Jankin. Perkin, the son of a plowman, attends school thanks to a parish priest who recognizes his potential. Adam later meets Perkin again at Oxford. Jankin, somewhat of a villain, wins Roger's war horse in a gamble. When the horse becomes lame, Jankin blames Roger and spitefully steals Nick. Adam's quest to find his dog takes him through various towns in southeast England.

The central theme of Adam of the Road is the significance of the individual. The author illustrates that across generations, everyone contributes to the tapestry of life. The same fundamental emotions that concern people today—love and hatred, loyalty and betrayal, kindness and cruelty—also concerned people in thirteenth-century England. While historical events and the past hold importance, people themselves are paramount. "A road's a holy thing," Roger tells Adam. "It brings people together."

An underlying theme is the importance of recognizing one's talents and choosing a suitable occupation. Adam encounters people from various trades and professions but ultimately decides to become a minstrel. Although a priest hopes to guide him into the clergy and a farmer wishes him to take up farming, Adam chooses his own path in life.