The family secret was to be passed down from one Collins generation to the next. The oldest child in the family was to receive the secret from the secret holder (701).
The secret regarded Barnabas Collins, who was a vampire and was locked in the secret crypt of the family mausoleum (705). It was assumed by most that the secret was about the location of the Collins family jewels.
The originator of the secret was Barnabas' father, Joshua Collins (460) who must have passed it on to Daniel Collins. Daniel would have passed the secret on to Gabriel Collins who passed it on to his wife, Edith Collins rather than their son, but may have skipped over Gabriel and gone directly to Edith. Edith said on her deathbed that she and Daniel hated each other and the secret made her life unbearable (706). We can assume their son was either dead or unavailable as Edith would have to pass it on to one of their four grandchildren before her death. Edith kept the secret for at least 34 years, and was determined to pass it on to Edward Collins before she died, but when Barnabas Collins himself showed up, she went into shock, exclaiming "I know what you are! You are the secret! Passed on from generation to generation. You were never to be let out. We have failed, we have failed!" (706).
Before she died, Edward's brother, Quentin Collins and sister, Judith Collins both tried to learn the secret from their grandmother, but Edith would only tell Judith that she would be happier not knowing, as it was "terrible" and she must not tell the others even that much (705). When Quentin threatened to kill Edith in order to deprive Edward of the secret, she told him "That would be very dangerous for you to do" (705). In her delirium near death Edith recalls people always saying "Don't tell Edith a secret, you know she will never keep it" (706).
When Edith died, Magda Rakosi was reading Tarot cards on Carl Collins and told him that Edith had just died, that she had not passed on the secret to Edward, and that someone knew what it was (706). Carl passed this information on Edward (707).
The secret was not discovered and was assumed to have died out with Edith Collins.
In 1840, when Barnabas made his first appearance and wished to be introduced to Daniel, it is obvious that Daniel had not been told the family secret. He was confused, believing it was the original Barnabas who had appeared, and made reference to Barnabas leaving for England. While it is possible Daniel, in his poor mental state, had forgotten the family secret, for the secret to have been handed down, he would have had to divulge it on his deathbed, something clearly not done.
Parallel time Edit
In the world of parallel time, both in the 1841 and 1970 versions, Angelique did not exist in the late 18th century, therefore Barnabas never became a vampire. Instead, he married Josette DuPres and live with her happily until his death in 1830. Therefore, the family secret never existed and it can be assumed that the secret room in the mausoleum did exist, but was not rediscovered until it became a home for Claude North in the 1970 PT sequence (1036).