As college students get dressed up for Halloween, ex-FBI agent Gregor Demarkian must catch a real campus ghoul before another faculty member is murdered.   Since Father Tibor Kasparian escaped the Soviet Union, he has done his best to keep his philosophy to himself--not out of fear, but because he knows that few people could stomach an honest account of life under Stalinism. When he gets an invitation to spend a semester teaching philosophy at Independence College, Kasparian hesitates, but his friend Gregor Demarkian, a former FBI investigator, convinces him to accept. They will both wish he had decided to stay away.   At Independence, Halloween is the biggest party of the year--it's also the anniversary of the day that the school's colonial founders pledged themselves to the American Revolution. As the students prepare to burn an effigy of King George, the hated professor Donegal Steele vanishes, and his secretary turns up dead. To keep his old friend from becoming the next victim, Demarkian will have to do his homework.