[GRASS5] shortest path with r.drain?

[benducke at compuserve.de]

How do I calculate the shortest path
_between two given points_
on a cost surface using r.drain?
The manual says to use the 'vector_points=start,stop'
Parameters, but when I do so,
all I get is flowlines down to the lowest
point from each of the points in both maps
, not a least cost path _between_ them.
Am I doing/thinking something wrong here?

Best,

Benjamin