On 25th January 1939, the day before Barcelona was seized by Franco's troops, Madame Perdomo (Julia Lahaye Jonckheer, Laken [Brussels] 1886 - Barcelona 1978), a Belgian nurse apparently settled in Spain from 1922, who had been convicted in absentia of spying for the Reich during World War I, played a crucial mediating role in guaranteeing the physical integrity of the Francoist prisoners of war from Montjuïc castle by commission of the ICRC delegates at Barcelona, as Marcel Junod highlighted in his memoirs (1951). Since 1937 she had been deeply involved in the organisation and managing of the Red Cross blood transfusion services at Barcelona throughout the entire Civil War (1936-1939), but shortly after her humanitarian mission in Montjuïc, Perdomo's trail was, to the best of our knowledge, lost until the publication of her obituary in 1978. Humanitarian action of individuals and aid organizations has been always modulated by differential beliefs, ideologies, socio-political agendas and gender; not to mention its potential instrumentation at the expense of other agendas above the humanitarian one. The examination of Madame Perdomo's diverse background as a spy and as a nurse, her leadership role in war situations and her experiences of care lead us to analyse her roles and practical choices, wonder about the eventual dilemmas and conflicts of loyalties she had to face as a humanitarian activist, and deconstruct gender stereotypes of women humanitarians/nurses traditionally depicted as white/loving angels.