Lt. Barclay's data transmitter opens a communications link from Earth to Voyager, whereupon the Doctor is used to find a cure for his dying creator.

Robert Picardo (Dr. Zimmerman)
Dwight Schultz (Lt. Reginald Barclay)
Marina Sirtis (Cmdr. Deanna Troi)
Tamara Craig Thomas (Haley)
Jack Shearer (Admiral Hayes)

• Building on the events in "Pathfinder", Starfleet will be able to send a compressed data packet to Voyager every 32 days, with a 17-hour window for Voyager to respond.
  
• The Doctor finds out that his EMH Mark-I program is obsolete, replaced by the EMH Mark-IV. The 675 EMH Mark-I's still in service were reconfigured to scrub plasma conduits on waste transfer barges. Zimmerman is a tad bitter that the EMH he created in his likeness has been delegated to the demeaning task.
  
• Barclay and Troi appeared earlier this season in the episode "Pathfinder". They will appear again in Season 7's "Inside Man".
  
• Admiral Hayes also appeared in the episode "Hope and Fear" and in the feature film Star Trek: First Contact.