A ruined castle to explore, long-derelict remains of an ancient war... where mysterious lights and legends of buried wonders have brought several bands to explore including your part... a perfect setting for some low level (1st-3rd) adventuring fun.
Apart from a general introduction there are no specific hooks to get your party in there, still a ruin with rumours of treasure should do the trick for any red-blooded adventurers. There's a clear map and good room descriptions with all the necessary details provided to run the adventure... including the other explorers, who are to be found at various points and tend not to be interested in collaboration!
In this company's usual style, there are a couple of photographs to illustrate the setting, useful for showing your players what their characters see (although my players are familiar with the castle gatehouse depicted: it's a location I know well and have been using in dungeons for some 30 years!).
This is an enjoyable low-level adventure that would feature nicely early in an adventuring party's career.