[Android] Mystery of Blackthorn Castle $0 (Was $4.89) @ Google Play Store

It does contains in app purchases, however you do not need them to progress in the game.

Once again your Uncle Henry has asked for your help in the search for a mysterious artifact. Embark on your own quest in this beautifully designed classic point and click adventure puzzle game. Explore an all but forgotten 14th century Blackthorn Castle, surrounding dark forest and structures. Discover hidden passageways, clues and puzzles along the way!