What's past

From Memory Beta: What's Past is the name for a six-part miniseries in the Star Trek: Starfleet Corps of Engineers eBook series. Conceived as a part of the Star Trek 40th Anniversary celebration, each of the six stories is set at various points across the Trek timeline.

From the back cover: A special six-part S.C.E. event that flashes back to previous adventures of the S.C.E. crew from the 23rd century to the height of the Dominion War, with special guests from all across the Star Trek universe!