Sheila Hancock (one of those amazing women who become more fascinating with age), is wonderful. Her young male co star is also good but she carries this off with her incredible eyes and amazing face, a real actress.
The script is just ok, nothing special. The journey is almost predictable but still worth watching and quite fun. The rest of the cast are really just filler who help to tell the story but aren't essentially needed to do more.
I had a couple of issues with the story, though. This octogenarian falls heavily twice and is momentarily unconscious on both of those occasions, seeming to hit her head badly both times. For a young person those two head-hitting falls might take a serious toll but apparently this old woman is tougher than superman and this doesn't seem to be a problem. The other issue is the one of inexperienced people traipsing into the wilderness alone... this one gets me very annoyed. It might make for cute story telling but utterly stupid behaviour like this usually ends in massive hunts requiring dumb people to be found... either dead or alive. Otherwise, the rapport between the two leads almost gets there in terms of something special, not quite, and it was a very pleasant watch in many ways.