About this "The Simpsons" episode:

The Simpsons - Raging Abe Simpson and His Grumbling Grandson in "The Curse of the Flying Hellfish" is the 22nd episode of season 7 and number 150 overall in the series.
In this episode the relationship between Grampa and Bart deteriorates and around the same time, one of Grampa's fellow-veterans of World War II dies, leaving Mr. Burns as the only other living member of Grampa's war squad, the Flying Hellfish. In the final days of the war, the unit had discovered several paintings and agreed on a tontine, placing the paintings in a crate, and the surviving member would inherit the paintings. As Mr. Burns wants the paintings as soon as possible, he orders Grampa's assassination and hire an assassin to do the job and to escape death, Grampa moves into the Simpsons house, where the family lets him live in Bart's room. Grampa reveals the secret of the treasure to Bart and the two manage to steal Burns' key and leave to get the paintings. They succeed, but are discovered by the State Department who give the paintings back to their rightful owner.