“Fata Morgana” is episode three of season one of Sanctuary.
Will agreed to join the Sanctuary in the previous episode, “Sanctuary for All: Part 2”, and Dr. Magnus told him that she was well over a hundred years old, and that Ashley’s father was John Druitt, her first patient and possibly Jack the Ripper.
Now, they are on an island in Scotland waiting outside a crypt guarded by some strange creatures called the Keepers of the Dead. Dr. Magnus says that inside the crypt is some sort of elixir capable of prolonging life for centuries.
When Will enters the crypt, some sort of mechanism is triggered and three sarcophagi open and a fluid drains away. Inside each is a young woman, all of whom are definitely alive, not dead. They are taken back to the Sanctuary (which may be on the western seaboard of the US).
When the women awake, they make statements suggesting that they are from 800 AD (despite speaking modern English and having perfect dentition). Will considers them to be crazy (because they speak perfect modern English; good to see that is covered) and that there is no way they can be as old as they say.
The removal of the women has not gone undetected. An ancient organisation, the Cabal, considers the women to be their property, and comes looking for them. Magnus believes that they are something called the Morrígan, and who bring death where they walk, finding them in Arthurian legends. The Cabal forces a confrontation with the Sanctuary; they are not happy about having their property stolen.