As we enter uncharted waters in terms of the outcome of the global crisis of capitalism that began in 2007, we might well ask if it represents a new global opportunity for labour and the subaltern classes more generally. In particular, I seek to address the complex and, sometimes conflictual, relations between trade unions and migrant workers. In the first instance, I pose the Challenges which migration represents for trade unions in the context of globalisation. More broadly, I examine the challenges for progressive social theory posed by the current global crisis. I then move on to the Mutations of the global system since the 1990s on the basis of Gramsci’s dictum that “the old has died but the new has not yet been born”. This is the necessary framework for the subsequent analysis of Workers in the context of the processes of globalisation and precarisation. My hypothesis is that we are now moving beyond the categories of North and South in terms of the mutations of capitalism and their impact on the workers of the world. Finally, I turn to the sometimes under-rated Complexity of the way workers are responding to the mutations of capitalism and thus posing a very real challenge to the stable reproduction of capitalist rule. I outline the limitations of a rights- based labour response to exploitation and the opportunities arising for a new multi-scalar global social unionism.