Barnabas, Quentin and the Magic Potion (January 1971)
This story marks a sudden shift in the characterization of Quentin Collins, who up to this point in the range had been portrayed as an enemy of Barnabas. Barnabas predicts trouble for Collinwood when Nicholas Freeze, in whose antique shop Carolyn Stoddard works, discovers a centuries-old potion that promises eternal youth. Soon after, Mr. Freeze's daughter, Hazel, tricked into taking a serum, dies. Carolyn is grief-stricken over her friend's death. Barnabas insists she stay on at the shop to watch Nicholas Freeze and his associates, one of whom Carolyn suspects is Quentin Collins, back at Collinwood in a disguise.

Then Carolyn sees Hazel's ghost.

She interprets this as a warning that Mr. Freeze has marked her for his next victim. Barnabas still refuses to let her quit.

Has Barnabas made a fatal mistake by deliberately endangering Carolyn's life? Or will his plan avenge Hazel's murder and put her spirit to rest?

Barnabas, Quentin and the Body Snatchers (February 1971)
In an alien spaceship hidden in a swamp near Collinwood, Roger Collins and his friend, space scientist Murdock Gray, lie bound and gagged—yet no one even knows they are missing! For their captors are able to change shapes at will, and two of them have "become" Roger and Murdock. Although Elizabeth and Carolyn sense a difference, they can't guess that they are at the mercy of beings who will stop at nothing to prevent the next U.S. space flight under Murdock's direction.

Then, as the dark shadow of death draws closer to Collinwood, a bat soars over the hidden spaceship, flies close enough to see inside… and suddenly Barnabas and Quentin Collins find themselves joined in a desperate attempt to save Collinwood from the strangest menace it has ever known!

Barnabas, Quentin and Dr. Jekyll's Son (April 1971)
Before the blizzard cuts Collinwood off from the rest of the world, Barnabas Collins arrives there from England, bringing with him his friend, Dr. Henry Jekyll, who hopes to find a new life where no one knows he is the son of London's most savage murderer.

Another stranger also finds refuge from the storm at Collinwood. He calls himself Paul Faron, private detective—but to Barnabas, he is Quentin Collins, victim of the werewolf curse.

As the personal tensions and animosities at the strange old house increase, a senseless, brutal murder takes place—and terror reigns at Collinwood. Obviously, the killer is someone living at the estate. And most under suspicion are Barnabas, Quentin and Dr. Jekyll's son.

As suggested by its title, a homage to Robert Louis Stevenson's 1886 novella, The Strange Case of Dr. Jekyll and Mr. Hyde, a text also used in the television series for inspiration.