Complex sentence: Roelfzema dropped off his friend Ernest de Jonge on Katwijk on February 22,1942 but he began to suspect there something was wrong with their operations, and grew suspicious that they were being betrayed by double agents among the government.
Split into simpler sentences: Roelfzema dropped off his friend Ernest de Jonge on Katwijk on February 22,1942. At the time he was beginning to suspect there something was wrong with their operations, and grew suspicious that they were being betrayed by double agents among the government.