Here is somewhat of a summary for Catching Fire. Since people have different views on what a spoiler is and isn't, I'm only giving you a brief summary.....Even with a summary, spoilers can still be present, but I hoped I helped!
Katniss is recovering from the previous book's events, where she and Peeta won the Hunger Games. Before Katniss, Peeta, and Haymitch leave town for the Victory Tour they're traditionally obligated to take, President Snow stops by to warn Katniss that he's watching her. He doesn't want to see any more rebellious stunts. Somewhat daunted, Katniss prepares for the tour.By the end of the tour, Peeta has publicly proposed to Katniss. Katniss is still worried that people can tell they're faking it, though. She begins to think of backup plans.
You can easily get a summary of the book "Catching Fire" online. The book stars with Katnis recovering from the events of the previous book where she won the Hunger games. More details about the summary can be found on the following site http://www.shmoop.com/catching-fire/summary.html.