Despite the best effort of industries and regulatory bodies employing and overseeing complex technical systems to mitigate failures, they are not always successful. In the current study, I examine the fatal accident at Lac-Mégantic in 2013, where a freight train carrying millions of liters of crude oil derailed resulting in the death of 47 people. Five years later, authorities have been unable to identify a root cause. To enhance our understanding of unexpected failures of complex systems and artifacts, I attempt to uncover the mechanisms underlying the accident. I first adopt the ‘defense in depth’ approach commonly employed in the industry and highlight its shortcomings. I develop an explanation centered on unrealized system drift, brought on by incremental deviations, normalized by boundedly rational agents adapting to local conditions. I propose the invisible hand of complexity steers the artifact undetected towards failure, and our limited understanding of complex systems impedes us from comprehending the implications of drift. I submit the regulatory response is unlikely to prevent similar accidents because our current ontological and epistemological framework to manage complex artifacts and investigate their failures is flawed. I develop theoretical and practical implications of my findings, and conclude with prescriptions to mitigate accidents.