THE HARDY BOYS (2 books) The Mark on the Door & The Secret of the Old Mill ~ Franklin W Dixon

THE HARDY BOYS (2 books) The Mark on the Door & The Secret of the Old Mill ~ Franklin W Dixon

2 Classic small paperbacks
Good condition

THE HARDY BOYS The Mark on the Door (Adventure 27)

While boating on Barmet Bay, Frank and Joe Hardy encounter a mysterious submarine and a suspicious man named Pancho Cardillo. Their investigation leads them to Mexico, where they uncover a sinister oil smuggling ring and a chilling mystery: villagers are disappearing, and a strange crest is being marked on their doors. With help from a local youth named Tico and their friend Chet Morton, the Hardy Boys confront danger in the desert and mountains of Baja California, ultimately exposing the man known as Pavuraterror in Spanishand solving the case

THE HARDY BOYS The Secret of the Old Mill (Adventure 16)

Frank and Joe Hardy stumble upon a counterfeiting operation while investigating strange happenings at an old mill near Bayport. A counterfeit $20 bill, a suspicious green van, and anonymous threats lead the brothers into a web of danger. As they follow clues and dodge sabotage attempts, they uncover a gang intent on derailing their fathers confidential mission. With help from their friends Chet Morton and Tony Prito, the Hardy Boys brave perilous encounters and unravel the secrets hidden within the mills shadowy walls