Correct, it is a SINGLE spirit. So if the body dies (from reduction to 0 POW or otherwise), the Shaman should still exist in the spirit world, and if they are the crafty sort should be able to find themselves a new... host(?), or if killed by someone, exact revenge, and then perhaps use their body as host.
If the Fetch dies (reduces to 0 POW), then the Shamans ability to travel the spirit world should be stopped, but their mortal self should be fine. Perhaps they live in a reduced state, perhaps they can find a way to awaken another fetch.
SDLeary