The Silent Three don their robes and masks.
"The Silent Three" was a strip that ran in School Friend (specifically, the revival that started in 1950). It was written by Horace Boyten and Stewart Pride and drawn by Evelyn Flinders.
The main characters were three schoolgirls named Betty Roland, Joan Derwent and Peggy West. Together, they formed a secret society devoted to foiling crooks, troublemakers and bullies, solving mysteries and finding treasure along the way.