Astérix et le Coup du menhir.

Due to an unfortunate accident involving Obelix throwing a menhir, Getafix the druid not only loses his memory, but goes completely mad. Now deprived of the wisdom of their beloved druid and the protection provided by his magic potion, the Armorican village falls prey to a proclaimed soothsayer who comes with ominous predictions and overweening ambitions. It's up to Asterix to keep his villager friends within reason and hopefully get Getafix to remember the magic potion's recipe before the impending Roman attack.