The play opens with the attendant Spirit explaining his purpose. He intends to teach virtue to mortals. He describes three travelers lost in the woods and remarks that the woods are dangerous and he is there to protect them. He says that the main danger to the three travelers is Comus, son of Circe and Bacchus. Comus has a liquor that turns human heads into animal heads:
Soon as the potion works, thir human countnance,
Th' express resemblance of the gods, is chang'd
Into som brutish form of wolf or bear
Or Ounce, or tiger, hog, or bearded goat,
All other parts remaining as they were, (68-72)
The attendant Spirit leaves when Comus approaches. Comus enters with his crew of monster-headed men and women, being loud and unruly. He quiets them as the Lady approaches. Her brothers leave her to find food and water. The Lady is worried about the noises she hears but decides to try to find help. Comus convinces her that he is trustworthy and proposes to lead her to the place where he saw the two brothers.
The scene shifts to the two brothers who discuss their hopes and fears for their sister. They meet the attendant Spirit, disguised to look like their father's shepherd, Thyrsis. The attendant Spirit tells them that Comus is with their sister and instructs them on how do deal with Comus. He says swords will be useless, so he intends to give them an herb (Haemony) which will ward off evil and allow them to break Comus' glass and steal his wand.
The scene shifts to Comus' palace. The Lady refuses his wine and can not leave. He keeps trying to convince her to embrace life's sensual pleasures. She continues to refuse and says that although he has imprisoned her body ("corporal rind"), he can not manipulate her mind:
Fool do not boast,
Thou canst not touch the freedom of my mind
With all thy charms, although this corporal rind
Thou has immanacl'd, while Heav'n sees good. (662-65)
The brothers rush in to the palace, break Comus' glass, and take care of his crew. Comus escapes with his wand. The attendant Spirit summons Sabrina to free the Lady.
The Spirit leads the three to Ludlow Town and the Presidents Castle where they are congratulated. The Spirit then leaves for Hesperus, and declares that any mortals that would follow him would be following the path of virtue:
Mortals that would follow me,
Love vertue, she alone is free,
She can teach you how to clime; (1018-20)