http://en.wikipedia.org/wiki/Third_Man_factor
The Third Man factor or Third Man syndrome refers to the reported situations where an unseen presence such as a "spirit" provides comfort or support during traumatic experiences. Sir Ernest Shackleton in his book South, described his belief that an incorporeal being joined him and two others during the final leg of their journey. Shackleton wrote, "during that long and racking march of thirty-six hours over the unnamed mountains and glaciers of South Georgia, it seemed to me often that we were four, not three."[1] His admission resulted in other survivors of extreme hardship coming forward.
