WOW, what an episode - my wife and I tried to remember for about an hour where we remember Fionula Flanagan's character from, and with a bit of help from the Lostpedia found the following:
Fionula Flanagan's character - she's from the episode "Flashes Before Your Eyes" (Season 3) - she's the 'shopkeeper' in the ring store who tells Desmond NOT to buy the ring for Penny, saying to him that it's his original fate not to buy the ring, which ends up leading him to the island and turning the key - She mentioned that if he doesn't do those things that "every single one of us is dead".
My guess about the island? Not only is it jumping in time, but also in location as well (hint: the pendulum marking various locations on a large map)...
Fionula Flanagan's character - she's from the episode "Flashes Before Your Eyes" (Season 3) - she's the 'shopkeeper' in the ring store who tells Desmond NOT to buy the ring for Penny, saying to him that it's his original fate not to buy the ring, which ends up leading him to the island and turning the key - She mentioned that if he doesn't do those things that "every single one of us is dead".
My guess about the island? Not only is it jumping in time, but also in location as well (hint: the pendulum marking various locations on a large map)...