Star Trek: Judgement Rites

Captain's log, stardate 6238.4. There is no doubt that you're being watched. By whom and by what type of life form is not determined. Even Spock has not been able to accurately assess this data. The occurrences are just too strange. Is that truly an ancient WW1 triplane heading straight for you at Warp 9? Could it be Trelane? How can your sensors suddenly report life forms on a dead planet?