Some knowledge — most infamously, the Nazi experiments on human subjects — has been acquired by means which cannot be morally condoned however beneficial the knowledge may be. Yet, given that we now have such knowledge, it seems morally questionable to forbid its use where we know it can benefit us. Although a strong utilitarian case exists for deploying such information and although any pragmatic, humane person would use it where it could improve a situation, residual moral qualms remain which are neither the expression of sentimentality nor squeamishness. Given the evil source of the knowledge, can we avoid the charge that we are tied to the evil, and even respectful of the experimenters, by wilfully benefiting from the work? I explore a few arguments meant to remove the moral qualms and show them all to be wanting. However, because we in fact regularly and routinely benefit in countless ways from many systematic evils of the distant past without qualms, we seem to be inconsistently selective when it concerns certain evils. This inconsistency can be explained, if not justified, by appeal to a principle of decent delay which allows us after a time to ignore the origins of our present benefits and so make moral fadeout acceptable. This principle itself is grounded in our natural and increasing forgetfulness of events as they recede in time, an adaptive mechanism which allows us both to carry on our lives in relative decency and yet to maintain a fitting sensitivity to newer, closer evils which affect more immediately our relations with others and our sense of moral integrity.