This is the background I would read or paraphrase for the players before beginning if this were a regular game.
Jes and Theo retrieved a saint’s relics from a supposedly haunted tomb in the hills above Zar Naf for the Cult of the Kingfisher. They encountered no danger, but are now somewhat trusted by the Heron-priest Maragon.
The Cult has recently risen from obscurity in the city. They gained the favour of the King by fortelling and uncovering a plot against the government by the Owl Cult. He now tasks them with giving him an accurate oracle of his intention to marry the Queen of Ru.
The Cult needs more cactus flowers for their divination†. They have a vague oracle of trouble in the desert. The caravan owner has a monopoly on bringing the flower into the city, and he distrusts the cult and refuses any outside help. Sama-Lan, the agent the cult sent to the desert, vanished. All other cult loyalists are needed to defend against threats in Zar Naf. So Maragon sends Jes and Theo with instructions to find Sama-Lan’s fate, and to make sure the cactus flowers get to the caravan.
In exchange, the cult will use their divination to find out the fate of Jes and Theo’s friend, Elira, and pay them 200 silver.
(† They use several different psychoactive herbs for their divinations, but there have been shortages of the other types, leaving them more dependent than usual on the cactus flowers.)