When something's lost to history, where does it go?

The seventh Doctor, Ace, and General Kramer visit a museum outside of time, where among the old masterpieces they find themselves faced with memories and old friends. But something else has set its sights on the museum's treasures...

For Those Who Came In Late...

Not seen "Time Rift"?  Don't worry, "Timeless" doesn't mention it.   But if you'd like to know who the unfamiliar faces are...