Based on the novel 'The Dark is Rising' by Susan Cooper, which is part of a series of five books collectively called 'The Dark is Rising Sequence'. 'The Dark is Rising' is in fact the second book in the series, and the first to feature the character of Will Stanton, who is arguably the hero of the rest of the series. The first book, 'Over Sea, Under Stone' focuses on three other children who play key roles in the sequence: Simon, Jane and Barney Drew, who also appear in two other books in the series: 'Greenwitch' and 'Silver On the Tree'. 'The Grey King' introduces Bran Davies who rounds out the cast. The only common character between the all five books is Merriman Lyon.
The five books are:
'Under Sea, Under Stone', 'The Dark is Rising', 'Greenwitch', 'The Grey King' and 'Silver on the Tree'.
The scene where Will is sent back in time to a viking raid was originally longer. Will was did not arrive in the middle of the raid but arrived moments before the vikings attacked, spotting them sneaking towards the village and having time to realize what was going to happen. The vikings and the villagers where mostly played by re-enactors who brought their own costumes. As it happens, actor Alexander Ludwig later found great success playing the viking Bjorn Ironside in History Channel's series Vikings.
Not related to the television series "Legend of the Seeker" or the "Sword of Truth" novels by Terry Goodkind, which "Legend of the Seeker" is based on.