At first Dissard worked under Ian Garrow, a soldier in the British Army, who had missed the Dunkirk evacuation and remained in France where he arranged an escape route over the Pyrenees. Although based in Toulouse it had key stations in Paris, Marseilles and Perpignan.
In October, 1941 Garrow was captured and imprisoned. Albert Guerisse took over at head of the network and when he was arrested, Dissard became the new leader.
As an elderly woman, the Gestapo did not suspect Dissard was a member of the French Resistance. She was able to travel around France to arrange for Allied airmen to get back to England. This involved escorting them to Toulouse where she arranged their lodgings. They were then moved to Perpignan where they were handed over to the Pyrenees guides.
In January 1944, one of the guides was arrested in Perpignan. Contrary to the rules of the network he was carrying a notebook that contained Dissard's name. She was now forced into hiding and lived in a variety of attics, cellars and garages in Toulouse until France was liberated.
During the Second World War Dissard arranged for over 250 Allied airmen to return to England. Of these, 110 were helped while the Gestapo were looking for her in 1944. After the war Marie Louise Dissard was awarded the American Medal of Freedom.