Star Trek: Judgment Rites

THE FIVE YEAR MISSION CONTINUES!Captain's Log, Stardate 6238.4. There is no doubt that you are being watched. By whom or by what type of life form is unknown. Even Spock is unable to make sense of the data. The occurrences are just too strange:

Is that really an ancient World War I triplane heading straight for you at Warp 9? How can your sensors suddenly detect life forms on a dead planet? Where did that primitive race obtain such advanced technology? No, it couldn't be Dr. Bredell of the Vardaine Science Counsel... he didn't survive your last encounter.