The following version of the book was used to create this study guide: Bajaj, Varsha. Thirst. Penguin Random House, New York, NY, 2022. Kindle AZW file

Minni is a 12-year-old girl who lives in a small house in an impoverished community in Mumbai, India. Ma does an enormous amount of work for the family and works as a maid in the home of a wealthy family in a nearby neighborhood. Minni's father (Baba) operates a tea shop. Her brother Sanjay is 15 years old and works at a local restaurant. Minni goes to school, studying hard in order to retain the option to continue her education. She spends a lot of time studying with her best friend Faiza.

Though her family faces many difficulties, one of the biggest challenges is carrying enough water from a public tap each morning to take care of the family's needs. The water is not safe to use without boiling and often stops flowing altogether during the day. Minni knows that the monsoon season comes later each year, meaning the local water levels have dropped. To make the situation more dire for the poor neighborhoods, a gang known as the water mafia has been stealing water. One evening, Sanjay's best friend Amit invites Sanjay, Minni, and Faiza to go for a ride in the car his uncle drives for a wealthy man. The uncle leaves the four children alone in the car for a short time. Amit leads the others into a dangerous situation that they realize is the work of the water mafia. A man named Ravi recognizes the boys but does not identify them. A man who is obviously in charge sees the boys and shouts at them.

The children know they have stumbled on a scene that puts them in danger. Since the water thieves only saw Amit and Sanjay, the adults decide to send them to a farm in the country. A short time later, Ravi turns up dead. Minni hopes this means Sanjay can return to the city, but the adults still fear that Ravi may have revealed Sanjay's and Amit's identity before he died.

Without Sanjay's help carrying water and his companionship, Minni's life changes. Her life changes more when Ma becomes sick. Unable to even stand without wobbling, she goes to her sister's home to recover. In addition to her chores at home and her homework, Minni begins to travel every afternoon to the home of Anita, the wealthy woman who is Ma's boss. She discovers that Ma had also helped Baba at the tea shop, meaning Baba now spends even more hours away from home. Minni begins to mature as she takes on her new responsibilities.

Minni is shocked when she discovers Anita's husband is the man who chased Amit and Sanjay while stealing water. She anonymously sends his identity to the police, but she is never entirely sure that it played a role in his arrest. Meanwhile, Minni learns Ma's illness is probably the result of a virus from drinking tainted water. The illness is entirely treatable. Ma returns home, but Sanjay has a new job cooking at a restaurant and decides to stay in the country. Other parts of Minni's life are changing as well, including that she is taking computer classes and joining an effort to clean up the neighborhood and the nearby river.