Obscure religious movements, restless unions, industrial spies, impetuous journalists, foreign conspirators or nationalist rising stars ... Between 1920 and 1961, the face of communism in the Congo was at the very least multifaceted. Its reality, its degree of dangerousness and its fight varied according to the political, economic, and social contexts of Belgium and its colony, but also according to the international arena's challenges, both in the East and the West. However, under these fluctuations we can detect several constants: hidden motives and aspects of the networks, recurring mental strategies and patterns will shape this fight against the red peril. Confronting archives, works and unpublished testimonies, Belgian, Congolese and international, and both from the liberal-capitalist and communist "edge", our historian and critical analysis demonstrates that, despite its failure to in fine establish itself in the Congo, communism had nonetheless had a surprisingly mobilising power by the impacts and achievements that its fear generated. This is why we can really talk about "the power of the absent". This influence is exerted in a host of areas, from police and military spheres - official and covert - to complex diplomatic and economic mechanisms, including of course the delicate political and identity issues. Using the concepts of "myth" in building a “communist Lumumba” or "scapegoat" as “crisis regulator”, our study concludes more broadly on human mechanisms at work in the identification of a destabilising enemy, and his elimination, supposed to bring a symbolic appeasement or a symbolic credit.