Barnabas, Quentin and the Sea Ghost (Dark Shadows #29) by Marilyn Ross
 
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(Pocket Books 1970)
164 p.
 
Irma, with the help of Barnabas, tries desperately to clear her father's name, and in doing so, stumbles upon a monster even more dreadful than the Quetzalcoatl.

Professor Gerald Collins returns to Collinwood from an archaeological expedition to Mexico with several crates of animals -- giant rats, poisonous snakes and rare lizards. His daughter, Irma, turns to Barnabas for help. She fears her father also brought back a Quetzalcoatl, the terrible, cursed feathered serpent of Aztec legend.

Suddenly, a mysterious murderer strikes at Collinwood, and a feathered serpent is reported flying over the area. The townspeople, already angered by the presence of Barnabas at Collinwood, now demand that Professor Collins turn his specimens over to a zoo before anyone else is killed.