Puzzle no. 281

Black to play. This is from Caruana-Adams, Dortmund 2013. Despite play being in an endgame Adams sacrificed a piece. His adventurous play was rewarded when he reached the following position and won quickly with a tactic. What did he play? Answers to me at The Spectator by Tuesday 3 September or via email to victoria@spectator.co.uk or by fax on 020 7681 3773. The winner will be the first correct answer out of a hat, and each week I am offering a prize of £20. Please include a postal address and allow six weeks for prize delivery.
 
Last week’s solution 1 Rxf8+
Last week’s winner John Thackray, Rochester, Kent