Singing Serpent is # 17 in the Three Investigators series.
"The Three Investigators become involved in witchcarft when they try to rescue a woman from the influence of snake worshipers. "
"A strange, shrill song echoes through the old Jamison mansion. The housekeeper flees from the estate, screaming in terror. Young Allie Jamison blames a houseguest, Mr. Ariel, for the spine-chilling noises. He's an odd little man who never sees daylight. And he holds some mysterious power over Allie's eccentric aunt.
"Allie asks The Three Investigators to chase Ariel away. But Ariel is protected by powerful forces - evil spirits and a singing snake! "
007384 
Price: 7.50 USD

Monster Mountain is #20 in the Three Investigators series.
An Alfred Hitchcock Three Investigators books in which that team of youthful sleuths "journey to the high slopes of the Sierra Nevada for an adventure which begins, simply, with a search for a missing key" . . . and finally leads to the truth behind the dark legends of a hermit and a monster.
Based on characters created by Robert Arthur.
Est Level: 3rd - 7th grades
007260 
Price: 4.95 USD

Missing Mermaid is #36 in the Three Investigators series.
"Missing: 5-year-old boy. Name: Todd Stratten. Last seen with pet dog at Fourth of July parade, Venice Beach. Boy known for wandering off, mischief. Could be anywhere. Kidnapping not ruled out. Mother frantic. Investigator with gift for gab needed to suss out oddball neighborhood. Also missing: ceramic mermaid. Fishy case. Just the thing for the Three Investigators!"
Age Level: Grades 3-7
007789 
Price: 5.95 USD