Geheimnis um... is a 5-book series with 5 released primary works first released in 1943 with contributions by Enid Blyton.
#1 of 14 in The Five Find-Outers
1943 • 14 Readers • 216 pages • 4.2
#4 of 14 in The Five Find-Outers
1946 • 12 Readers • 227 pages • 4.1
#8 of 14 in The Five Find-Outers
1950 • 11 Readers • 160 pages • 4.6
#9 of 14 in The Five Find-Outers
1951 • 11 Readers • 180 pages • 3.6