Given the question: Generate a question that has the following answer:  Mr. Harley.  for the following movie plot:  When a flying saucer lands in Washington, D.C., the Army quickly surrounds the spaceship. A humanoid (Michael Rennie) emerges, announcing that he has come in peace. As he advances, he unexpectedly opens a small device and is shot by a nervous soldier. A tall robot emerges from the saucer and quickly disintegrates the soldiers' weapons with an energy ray. The alien orders the robot, Gort, to stop. He explains that the broken device was a gift for the President, which would have enabled him "to study life on the other planets". The alien is taken to Walter Reed Hospital, where he reveals his name: Klaatu. After surgery, Klaatu uses a salve to quickly heal himself. Meanwhile, the military is unable to enter his saucer; Gort stands outside, silent and unmoving. Klaatu tells the President's secretary, Mr. Harley (Frank Conroy), that he has a message that must be delivered to all the world's leaders simultaneously. Harley tells him that such a meeting in the current political climate is impossible. Klaatu suggests that he be allowed to go among humans to better understand their "unreasoning suspicions and attitudes". Harley rejects the proposal and leaves Klaatu under guard. Klaatu escapes and lodges at a boarding house as "Mr. Carpenter", the name on the dry cleaner's tag on the suit he "borrowed". Among the residents are young widow Helen Benson (Patricia Neal) and her son Bobby (Billy Gray). The next morning, Klaatu listens to the boarders speculate about why the alien has come. While Helen and her boyfriend Tom Stephens (Hugh Marlowe) go out, Klaatu babysits Bobby. The boy takes Klaatu on a tour of the city, including a visit to his father's grave in Arlington National Cemetery; Klaatu learns that most of those buried there were killed in wars. The two visit the Lincoln Memorial, then the heavily guarded spaceship. Klaatu asks Bobby who is the greatest living person; Bobby suggests Professor Barnhardt (Sam Jaffe), who lives in the capital. Bobby takes Klaatu to Barnhardt's home, but the professor is absent....
The answer is:
Who does Klaatu tell that he has a message ?