Who are the 'they' referred to in the letter on the website?

from Movie FAQ – Donnie Darko on Rap Genius

Meaning

In the letter to Elizabeth Hartford of the Rare Books Dept. of the Library of Congress, Karen P. Monnitoff (presumably Karen Pommeroy having married Kenneth Monnitoff) states that the Philosophy of Time Travel is being sent to Ms Hartford on specific instructions from her husband in the event of his untimely death.

Karen states that Ms Hartford would know where to put it — a place where they can never find it. The website alludes to Dr Monnitoff’s work with the CIA previous to being a teacher.

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