The Thorn is an ADRIFT 4 interactive fiction game and is © 2003 by Eric Mayer.
Review by David Welbourn (originally posted at Baf's Guide)
More of a short story than a game, you play someone in search of a mysterious thorn bush that has an obscure religious significance. Puzzles are almost non-existent; the main exception is the need to ask the NPCs about specific topics in order for the plot to continue. But after you've found the thorn bush and learned what it does, you may wish you hadn't. You'll have a choice to make, and only you can decide if you made the right decision.
Note: this game was originally written in ADRIFT for the Davidw's Minicomp 2003, and later ported to Inform. I've only played the Inform version.