I was in a very tight downstream siphon and didnt want anyone behind me. Main and McFaden, who were swimming, had gone to survey about two hundred feet of line that McFaden and I had laid a week or two before. On the day of McFadens death I had finished my dive and was on my way out when Bill Main signaled me from the downstream section. George incorrectly (and rather callously) stated that McFadens buddy (Main) left him. Main had emerged from a low silty area thinking McFaden was right behind him. He turned and waited for McFaden, but McFaden did not come. At this time he had only been waiting a few seconds and did not think there was a problem, but wanted me to hang out just in case. I got a bad feeling and some instinct made me elect to enter the area. I found McFaden within 100 feet, off the line, not moving. I led him out and just as we emerged into clear water he signaled out of gas. Keep in mind, McFaden has been missing for one to two minutes and is already out of gas? I gave him my long hose and I could hear him breathing like a horse and knew he was scared. He grabbed my manifold like a vise and I hit the trigger. We got to a vertical pit and I stopped motoring and started venting my dry suit. Suddenly I realized that even though I was venting as fast as I could we were ascending rapidly. McFaden would not let go of my manifold to vent his suit. Next thing I knew I was pinned like a bug to the ceiling. I couldn't get him to let go of my manifold so I could even turn around. I finally had to use the scooter to pull us back down so we could continue out. During the entire exit, Bill Main had hold of McFadens legs, trying to pull him down by getting as negatively buoyant as he could. By the time we got near the entrance I ran out of gas. I was seconds away from passing out when Bill Main starting buddy breathing with me on his short hose. By now Bill had already given his long hose to McFaden. Bill Main never hesitated to share gas with both of us, even if it meant buddy breathing off a short hose. At this point my head was a ball of screaming agony from carbon dioxide build up. I could barely do anything but try to catch my breath. After a minute or so I noticed Bill Main picking his long hose up from the floor. He grabbed my arm and pulled me out of the silted out bedding plane area back into the cave. I was screaming into my/his regulator because I DID NOT want to go back INTO the cave, but he was taking us to clearer water. Off to the left I saw McFaden upside down on the ceiling, pressed there by his dry suit, apparently dead. (The preliminary autopsy report indicated that he had embolised. I would guess that this occurred during the rapid ascent from the pit at 180 feet or during the final ascent across the last room.) Once in clear water, we stabilized our situation, swapped second stages so I would be on Mains long hose, relocated the line and made our exit. When I broke down my gear later you could take my regulators off the manifold without even closing the valves. I did everything I could for McFaden and so did Bill Main and we both nearly got killed. Make absolutely no mistake - trying to rescue a panicked diver is one of the most dangerous things you can attempt.