The Dagger in the Sky (Doc Savage #40)

"Three times the dagger had appeared - destroyed - then disappeared! Three times the knife of KUKULKAN hung in the sky, 200 feet tall, while death struck. The Man of Bronze stalks the dark secret of the blade; a quest that takes him deep into the jungle to the very edge of doom! * To the world at large, Doc Savage is a strange, mysterious figure of glistening bronze skin and golden eyes. To his amazing co-adventurers - the five greatest brains ever assembled in one group - he is a man of superhuman strength and protean genius, whose life is dedicated to the destruction of evil-doers. To his fans he is one of the greatest adventure heroes of all time, whose fantastic exploits are unequaled for hair-raising thrills, breathtaking escapes and bloodcurdling excitement."