On the night of 6 April 1944 Mertizen was dropped by parachute with two other women agents (Marie-Louise Cloarec and Pierrette Louin). After landing in a field in the Limoges region of France the three women made their way to Paris.
On the night of 25 April, the women were arrested after being denounced by a collaborator and interrogated by the Gestapo. In August they were transported to Ravensbrûck concentration camp where they were shot, and their bodies incinerated sometime in 1945. Mertizen was posthumously awarded the Military Cross, Medal of the Resistance and the Chevalier of the Legion d’honour. Her name will be found on the Tempsford Memorial in Bedfordshire near former RAF Tempsford (138 Special Duty Squadron) which was responsible for parachute operation in occupied Europe. (I’m still researching the other women).