Player wants to ditch party

My party right now is trying to navigate their way past herds of Gorgons (the petrifying bulls) to get to a mission destination. One of my players, playing his character, knows what these are and doesn't want to proceed. He is willing to head back to camp and let the party continue on without him. What do I do with him during the session? Just let him relax and listen in on what everyone else is doing?

EDIT: I didn't fully explain in the op or as a reply to any of the comments because it would be a lot of detail to explain. But I guess now is as good a time as ever. I've learned a LOT from y'all's feedback. THANK YOU ALL Please don't take my list as being rude, it's just how I process thought: 1. I change focus/ scene all the time with this group because they like to split party in towns and more. So if he wanted to go back to camp he could. 2. The camp is a research camp, so it's full of people. (The mission is to save one of the archeologists that went past the dig site)(This lost archeologist ultimately found Medusa and got stoned) 3. If he did go back to camp, I was planning on having the research crew finding a mirror that was to be used in the ancient war all those ages ago. I figured this would have him rushing back to the party to aid them in their fight against a Medusa. (Which would ironically have him now pass the herd of gorgons alone (though honestly that might work in his favor)) 4. I've talked to the player since this post. He explained that his character is scared shitless of these things. Him being a long range fighter wants as much distance between him and any major threat like this. He does plan to "leave" the party, but just to create that distance where he is better suited to assist the party.