If you don't want to know the circumstances surrounding March 10th's entry in this slideshow, then don't read any further...
[spoiler]March 10th's quote:
Ep #1086 (1970) - Hallie - 'No, David, we MUSTN'T! We MUSTN'T!'
From "#1086/1087: Robservations 08/29/03: Murderous Gerard"
As Tad and Carrie stand on a mysterious staircase, beseeching them, come into the room!, David asks Hallie, take my hand. No, she says, we mustn't go to them. They're calling us! objects David. And while the two of them argue what to do, Tad and Carrie disappear. They're gone, says David, where did they go?
The Robservations sort of references the quote, but Hallie's line is delivered as quoted and she doesn't say anything about not going to them...
And since the forum was offline, here's the graphic for the quote:
And this is the second quote from this ep. The first (Hallie - 'Oh, we've got to be careful. They MUSTN'T ever find out') was back on February 10th.