1) Background: Consumers’ response to threat is an important topic and needs further exploration, especially in times of Covid-19 pandemic. This paper contributes towards widening its understanding from the perspective of consumers’ purchase behaviour in the context of convenience stores. It adds to the debate on the influence of the Covid-19 threat and all unprecedented pandemic circumstances (exogenous and endogenous impacts) on consumers’ purchase routines and habits. 2) Methods: This study analyses a unique dataset of transactional data (783,502 observations) drawn from 1,291 convenience stores located in the United Kingdom (thanks to The Retail Data Partnership Ltd). The captured period includes 36 months (from January 2018 till December 2020). This panel data study concentrates on the particular aspects of purchase behaviour (one item transactions, average spend per transaction) in the pre-pandemic and pandemic period. 3) Results: This investigation reveals that the share of one item transactions fundamentally decreased in the analysed pandemic period (especially in April 2020) both in the overall number and value of transactions. The average transaction (basket) value increased in that period. Further analysis concerning the stores’ location, affiliation and size adds depth to our contribution. 4) Conclusions: Our findings show the meaning of convenience sector in times of threat. We demonstrate specific aspects of the claim that purchase behaviour habits and patterns have significantly changed in the era of Covid-19 pandemic. Understanding this change underpins the long-term process of knowledge building in the field of consumers’ purchase behaviour. It also makes business practitioners, policymakers and consumers more proactive than reactive in the case of future.