Three Knocks at the Crypt Door

From publisher blurb: Adventure for characters level 3 through 6 for Swords & Wizardry A fire breaks out in the Temple of Balance. Two of the three clerics who care for the temple are found dead after the fire is put out and the third is missing. An anicent door into the vaults of the temple has been broken open ... from the inside. Can the party discover the reason behind the fire and what happened to the third cleric?