Unlike Bellairs's other novels, The Treasure of Alpheus Winterborn does not use the supernatural as part of the plot. The narrative follows a search by its young hero, Anthony Monday, for a treasure hidden by a long-dead eccentric millionaire. Despite the fact that Anthony is trying to help his family out of financial difficulties, there are some disturbing moral questions involved in the way Anthony goes about seeking the treasure. Bellairs himself calls the novel an "odd book," whose creation was motivated by his desire to write a story that recalled his own family life. Perhaps because of the strong autobiographical element, this story, particularly its plot, is somewhat more uneven than his other novels.
Nevertheless, the novel displays Bellairs's essential strengths. Typically, Bellairs's greatest virtue has been his ability to create young protagonists whose weaknesses and vulnerabilities make them believable. Anthony Monday's constant fretting over his family's financial difficulties, added to his own lack of self-confidence, makes it easy for young readers to identify with him. Yet when Anthony faces personal danger, he manages to call up his courage, confront the peril, and do what must be done. Bellairs consistently creates "heroes" flawed enough for his young readers to identify with, yet successful enough for them to emulate. In this way his novel offers an effective combination of realism, adventure, and moral value.