Author: Dawson, Mark, Mantle, Ben
Interest age: from c 8 years 
Published 23/06/2022 by Hachette Children's Group (Welbeck Children's Books) in the United Kingdom as part of The After School Detective Club series 
Paperback | 240 pages, 30 b&w illus
The second in a series of gripping adventure stories for readers 8+, perfect for fans of Enid Blyton.
The friends can't believe their luck when they get the chance to stay in a castle for their Easter holidays.
The castle is everything they had hoped for, with a moat and an ancient burial mound that gives it an air of mystery. But things are not what they seem and a treacherous discovery in the grounds reveals a 300-year-old treasure map.
The race is on. The After-School Detective Club is in pursuit of Ragnar's gold – a hoard of treasure said to have been buried by a Viking warrior and guarded by his demon hound... that is, unless someone else gets there first.