Gao Guang didn't know what the big deal was, but he didn't want to join. However, without joining, there was no way to know what the big deal was. It was a vicious cycle, an unsolvable problem.
From a cost-benefit analysis, Gao Guang already had two hundred and seventy thousand US dollars. This was already a fortune, and he didn't want, nor need, to risk his life for more money.
Additionally, knowing too much made it hard to extricate oneself, so Gao Guang didn't want to get involved in some obscure big deal.
But now Gao Guang knew too much, so could he refuse? The answer was clearly no—he couldn't refuse since circumstances dictated his actions.
Human nature is not to be delved into deeply. Even though he had gotten along well with Frank and the others so far, and had made a fortune with them, Gao Guang really didn't know what the consequences of refusal would be.
So there was only one correct answer.
"I am willing to join you!"