Titles in the Original Hardy Boy Series

Source: Wikipedia.

1. The Tower Treasure
2. The House on the Cliff
3. The Secret of the Old Mill
4. The Missing Chums
5. Hunting for Hidden Gold
6. The Shore Road Mystery
7. The Secret of the Caves
8. The Mystery of Cabin Island
9. The Great Airport Mystery
10. What Happened at Midnight
11. While the Clock Ticked
12. Footprints under the Window
13. The Mark on the Door
14. The Hidden Harbor Mystery
15. The Sinister Signpost
16. A Figure in Hiding
17. The Secret Warning
18. The Twisted Claw
19. The Disappearing Floor
20. Mystery of the Flying Express
21. The Clue of the Broken Blade
22. The Flickering Torch Mystery
23. The Melted Coins
24. The Short-Wave Mystery
25. The Secret Panel
26. The Phantom Freighter
27. The Secret of Skull Mountain
28. The Sign of the Crooked Arrow
29. The Secret of the Lost Tunnel
30. The Wailing Siren Mystery
31. The Secret of Wildcat Swamp
32. The Crisscross Shadow
33. The Yellow Feather Mystery
34. The Hooded Hawk Mystery
35. The Clue in the Embers
36. The Secret of Pirates' Hill
37. The Ghost at Skeleton Rock
38. The Mystery at Devil's Paw
39. The Mystery of the Chinese Junk
40. Mystery of the Desert Giant
41. The Clue of the Screeching Owl
42. The Viking Symbol Mystery
43. The Mystery of the Aztec Warrior
44. The Haunted Fort
45. The Mystery of the Spiral Bridge
46. The Secret Agent on Flight 101
47. Mystery of the Whale Tattoo
48. The Arctic Patrol Mystery
49. The Bombay Boomerang
50. Danger on Vampire Trail
51. The Masked Monkey
52. The Shattered Helmet
53. The Clue of the Hissing Serpent
54. The Mysterious Caravan
55. The Witchmaster's Key
56. The Jungle Pyramid
57. The Firebird Rocket
58. The Sting of the Scorpion