Paraphrased:

The narcissist’s smirk is a subtle but telling expression that occurs when a narcissist experiences pleasure from manipulating or deceiving someone.

For narcissists, the smirk usually reflects contempt, which is a deep-seated disdain or lack of respect towards others. For narcissists contempt is tied to their belief in their own superiority. They view others who do not serve their needs as worthless or beneath them, showing a complete disregard for how their actions impact those around them.