'Forgive And Forget' is a good episode. In it we meet Riley's old rival. He tried to use his energem to cheat, but it backfire on him. Meanwhile the big bad has created a plan to make people forget who they are by tainting the water wit a memory eraser venom. It almost work, but Riley having his own energy drink. As a result, The Purple Dino Charge Ranger created an antidote which allow the rangers to get their memories back and destroy the monster again.
