Geheimnis um... is a 5-book series with 5 primary works first released in 1943 with contributions by Enid Blyton.
#1 of 15 in The Five Find-Outers
1943 • 12 Readers • 216 pages • 4.1
#4 of 15 in The Five Find-Outers
1946 • 5 Readers • 227 pages • 3.7
#8 of 15 in The Five Find-Outers
1950 • 6 Readers • 160 pages • 4.5
#9 of 15 in The Five Find-Outers
1951 • 3 Readers • 180 pages • 4.5