Rating: not given at Teaspoon, but at ff.net it's Teen.
Author's summary: The Doctor's plan to involve his companions in an interesting project leads them all into a perilous situation that will prove to be a test of each one's personal strengths.
Characters/Pairings: Fifth Doctor, Adric, Nyssa, Tegan
Recced because: I love Fifth Doctor adventure fics, and Patrice has written several excellent ones. All are well worth reading, but I settled on this particular one because it has especially good characterization of Adric. While exploring a seemingly peaceful planet, Adric quickly manages to become separated from the others and finds himself in a dangerous situation. Of course, Doctor, Nyssa, and Tegan don't fare very much better during their search for him, so all four have their problems. The alien world is interesting and the resolution is believable, making this story a highly satisfying read.