According to Boin et al, a crisis—whether political, environmental, financial or (in this case) public health—has three defining features: uncertainty, urgency and threat. In this lecture, I will consider how these features shaped and constrained the response of implementation science to the Covid-19 pandemic. Using illustrative examples of major service innovations implemented at pace and scale in the early months of the pandemic, my theoretical focus will be three themes that have long interested implementation science researchers. First, the challenge of “spread and scale-up” (that is, moving from a promising innovation that has been shown to “work” in a small demonstration study to a new way of working that becomes business-as-usual – i.e. acceptable, affordable, feasible and the expected way of working – across the board). Second, the challenge of balancing standardisation (where everyone implements the same innovation) and local embedding (in which technological solutions, policy directives or national guidelines must be flexed and negotiated to accommodate the different contingencies and path-dependencies of different settings). Third, the tension highlighted by Robey and Boudreau between two different logics: on the one hand, the logic of determinism – a conceptual orientation whose roots are in the hard sciences and which is innovation-centred, causal and more or less linear (as in “the impact of innovation X on outcome Y”), with context viewed as an external milieu of mediating and moderating variables; and on the other hand, the logic of opposition – an orientation whose roots lie in the critical social sciences, which eschews the search for linear, cause-and-effect relationships between variables and instead views reality as fluid, dynamic and containing inherent and unresolvable tensions, some of which inevitably generate conflict. The lecture will conclude with some suggestions for preparing for the next crisis.