The naming of the characters in this Tale is riddled with satirical nomenclature: Januarie, the main character, is named in conjunction with his equally seasonal wife May, representing their individual characters: January is 'hoor and oolde', sharing the bare and unfruitful characteristics of his title month, whereas his youthful and 'fresshe' wife represents the spring seasons. This has particular relevance when considering the parallel between this tale, and the Biblical tale of Adam and Eve. Januarie's brothers are named Placebo and Justinus: the former a sycophant, whose name in Latin means 'I will please', and the latter a fairer man with no individual motive.
The main character, Januarie (or January) (a senex amans), is a 60-year-old knight from the town of Pavie, in Lombardy. Pavie was a place known for having many banks and brothels (thus revealing certain characteristics about both the merchant and Januarie).
When Januarie decides that he wants to marry, he consults his two brothers Placebo, who enourages him and Justinus, who opposes marriage from his own experience. Januearie, a vain man, hears only the flattery of his pleasing brother Placebo.
Januarie marries May, a teenage girl, largely out of lust and under the guise of religious acceptablilty. It is unknown why May accepts Januarie; however, it is safe to assume that she did it for social betterment and possibly some kind of inheritance, Januarie being a rich man.
A squire in Januarie's court, called Damyan, falls in love with May and writes a letter to her confessing his desires. She becomes intrigued by this man and plots to have sex with him. Januarie is struck blind shortly after he is married, although it is not explained why, though Chaucer's suggestion is that his vanity, lust and general immorality have rendered him both morally, and literally blind. This disability, however, spiritually serves Januarie well. His language and character, formerly lewd and repulsive, becomes beautiful and gentle love poetry, and his love for May evolves to more than just lust and desire. On June 8, Januarie and May enter a garden that he has built for her (suggestions arising both from traditional romantic literature and, of course, The Old Testament's Garden of Eden). Meanwhile, Damyan has sneaked into the garden using a key he has made from a mold May has given him and waits for May in a pear tree, symbolising, it has been said, the forbidden fruit from Genesis. The Biblical relevance of The Merchant's Tale allows it to become more than just a bawdy fabliaux, but a reinforcement of age-old Christian morality.
May requests a pear from the tree and Januarie, old and blind, and therefore unable to reach, stoops to allow May to climb onto his back herself. Here Chaucer evokes enormous pathos for the 'hoor and oolde' January, soon to be cuckolded by a manipulative female figure, a clear reversal from the horrific and repulsive figure painted by the narrator in the opening presentation of the man. In the tree, May is promptly greeted by her young lover Damyan, and they begin to have sex, described by the Merchant in a particularly lewd and bold fashion: 'And sodeynly anon this Damyan / Gan pullen up the smok, and in he throng.' Indeed, the narrator does apologise for this explicit description, addressing the pilgrims saying: 'Ladyes, I prey yow that ye be nat wrooth; I kan nat glose, I am a rude man --'
Two Gods are, at this moment, watching the adultery: Pluto and 'Proserpina' (or 'Proserpyne'). They begin a passionate argument about the scene, in which Pluto condemns women's morality. He decides that he will grant Januarie his sight back, but Proserpina will grant May the ability to talk her way out of the situation, saying, "I swere / That I shal yeven hire suffisant answere / And all wommen after, for hir sake; / That, though they shulle hemself excuse, / And bere hem doun that wolden hem excuse, / For lak of answere noon of hem shall dien."Indeed, Proserpina's promise that 'alle wommen after' should be able to excuse themselves easily from their treachery, can be seen as a distinctly anti-feminist comment from the narrator, or perhaps even from Chaucer himself. These presentations of these two characters and their quarrel exposes many elements of the tale, namely the argument between man and woman and the religious confusion in the tale which calls of both the ancient and the Christian Gods. Indeed the presence of these particular Gods has individual relevance when related to this tale: as the legend goes, Proserpina, a young and much loved Goddess, was stolen and held captive by Pluto, the King of the Underworld, who forced her to marry him.
Januarie regains his sight just in time to see his wife and Damyan engaged in intercourse, but May successfully convinces him that his eyesight is deceiving him because it has only just been restored and that she is only 'struggling with a man' because she was told this would get Januarie's sight back.
The tale ends in an unorthodox manner: the fooled Januarie and May continue to live happily with the promise of a baby soon to be born. However, Chaucer does not end the tale entirely happily: a darker suggestion is there, as May tells Januarie that he may be mistaken on many more occasions ('Ther may ful many a sighte yow bigile'), indicating that, perhaps, her infidelity will not stop there.