A feisty heroine, a stalwart hero, two enemy groups of ancient origin, appropriate deaths for nature's despoilers, world-wide canvas and pointed reminders of earth's fragility should add up to commercial success. But in Morrell's ( The Fifth Profession ) latest thriller the ingredients don't produce a satisfying dish. Environmental writer Tess Drake is chasing both a story on fatal attacks on polluters around the world and a strange man named Joseph. Aided by NYPD Lt. Craig, Tess discovers that Joseph has been burned to death; in his apartment she and Craig find strange artifacts that point to Albigensian heretics, worshippers of ancient god Mithras. After suggesting that the followers of Mithras and agents of the (still vital) Inquisition remain in lethal combat, Morrell sets the Mithras baddies against Tess. She and Craig fall in love and are entrapped by the boyish U.S. vice-president, a chief bad guy. By the bloody climax in a Spanish cave readers will be thoroughly tired of the book's padding and cardboard characters. 100,000 first printing; Literary Guild and Doubleday Book Club alternates; author tour. (May)