The story takes place over the course of a single day and follows the interactions between a group of characters who have gathered for a weekend house party on a houseboat in the Mississippi River. The main character, a writer named John, spends most of the day contemplating his failed relationships and his place in the world. The other guests include a wealthy couple, a painter, a journalist, and a pair of actresses.

Throughout the day, the characters engage in various conversations and activities, revealing their complex personalities and relationships with each other. Faulkner uses his signature stream-of-consciousness writing style to explore the inner thoughts and motivations of each character. The novel also delves into themes such as love, betrayal, and the search for meaning in life. As the day progresses, a storm approaches, and tensions among the characters begin to escalate.

"Mosquitoes" is considered one of Faulkner's lesser-known works, but it is notable for its experimental style and its exploration of complex psychological themes. This novel has been praised for its insightful portrayal of the human condition and its use of language to create a vivid and immersive reading experience.