Cruel Summer expands on the summer arc of Waterdeep: Dragon Heist, adding two new factions, several colorful new NPCs and four new mapped locations. After the Cassalanter's Founders' Day celebration ends in death and destruction, their twin children are found to be missing. Waterdeep is in an uproar, the Cassalanters aren't talking and it falls to the party to solve the mystery of the childrens disappearance. Could it be connected to the sinister new faction taking root in the city? Who is the stranger whose corpse was left behind in the twins' bedroom? Is there a link to the surprisingly vicious Noble Council of Soapmakers? With this supplement, the PCs will have a chance to save the Cassalanter children from the terrible fate outlined in Dragon Heist, avoiding the "Trolley Dilemma" situation some players might not enjoy. It also incorporates elements of the Spring, Fall and Winter arcs, allowing the players to rub shoulders with Jarlaxle, Manshoon and the Xanathar.