This essay considers the circumstances of persons deprived of their liberty in the context of Covid-19. Detention is always intended to be exceptional and the essay explores the extent to which the pandemic impacts upon this exceptional character. First, by increasing the unacceptability of detention, have the rules regarding what may constitute “arbitrary detention” changed? Secondly, for persons serving out prison sentences, to what extent should Covid-19 serve as a justification for early release or commutation of punishment? In this respect, should the goals of retribution and specific and general deterrence be weighed against the rights to health and safety of prisoners and prison staff, and if so, how? Do detaining authorities have absolute discretion to determine which detainees to release or must they ensure that policies of release also, are not arbitrary? To what extent does the arbitrary resort to detention as well as the arbitrary decision to maintain someone in detention during the pandemic, which may heighten certain individuals’ exposure to the disease and thereby produce extreme anxiety, give rise to cruel, inhuman or degrading treatment or punishment, if not torture? The paper considers how governments, specialist agencies and courts are beginning to grapple with these legal, ethical and public health issues. On the one hand, recognition of the heightened health risks for detainees associated with the pandemic is proving to be an important opportunity to reduce reliance on detention – and thereby to make good on the intention for detention to be recognised as an exceptional measure. Yet on the other hand, as will be shown, the selectivity of approaches and lack of transparency and oversight of decision-making has put some detainees at even greater risk of harm