Based on years of immersion as an ally in Chicago and Brussels, this transatlantic ethnography offers an unprecedented inside look into the birth, growth, and demise of undocumented-led organizations. In cities on opposite sides of the Atlantic, migrants struggled to create a space from where they could speak their own truth as lived experiences of illegality reinforced their feelings of powerlessness. But as Swerts reveals, under certain conditions, vulnerabilities can be developed into collective strengths. By openly sharing their stories, contesting restrictions on mobility, and publicly expressing their emotions, undocumented activists expose the hidden reality of 'Citizen X'.