She saw a wild raccoon walking up, but then she noticed the poor thing was blind in both eyes. The raccoon had some eyesight, but was very limited, but when she saw what the kittens were doing, her heart melted.
The black kittens saw the raccoon in need of some help and they decided to be his bodyguards all around the yard. This happened for over 5 years which is a very long time for the raccoon to live! (especially since he was blind)