"Shikamaru's Genius" (シカマルの才, Shikamaru no Sai) is episode 86 of the Naruto: Shippūden anime.
Hidan stabs himself in the chest, but instead of mortally wounding Shikamaru, he destroys another one of Kakuzu's hearts. Shikamaru reveals to have poured Kakuzu's blood that Kakashi had retrieved earlier in a capsule on Hidan's spear, and so he had killed one of Kakuzu's hearts. He also traps Hidan with his Shadow Imitation Technique. Being temporarily incapacitated, Kakuzu's remaining three hearts return to his body, with one sacrificing itself to become his heart. Just as Kakuzu is about to finish them off with another fire-wind technique, Team 7 arrives just in time to stop the attack with Naruto and Yamato's wind-water techniques combo.