Candace’s gelatin party inspires Phineas and Ferb to use Isabella's swimming pool for making gelatin. Doofenshmirtz invites Agent Perry the Platypus over for tea. The diabolical doc made a devilish device that can make anything evil. Doc tried to zap A.P. with this ray. A.P. dodged so the ray zapped the gelatin. It turned evil and came to obey doc. The gelatin monster grabbed A.P. who threw his hat at the fire-extinguisher sprinkler. The water dissolved the gel and also fried the electronics in doc's zapper hence ruining doc's plans. / While in London, Candace and Stacy emulate Sherlock Holmes and Dr. Watson, while trying to bust Phineas and Ferb. Meanwhile, Perry must team up with British agent Double-0 0 in order to stop Dr. Doofenshmirtz from moving Big Ben to the Tri-State Area.