Read Ayn Rand's Capitalism: The Unknown Ideal. She will answer many questions regarding Capitalism.
Rand did comment on Smith's concept of trading guided by an invisible hand. Rand dismissed the invisible hand concept due to the fact that it implied men are guided by some mystical power, rather than their own volition.
There is no third party in capitalism - neither an invisible hand, a government, a king, or a man holding a gun to your head. Capitalism includes only traders voluntarily exchanging value based on their rational self-interest.