A Mama cat heard a motherless puppy crying !
When motherless puppy started crying the cat did not think twice. Kitty rushed to rescue without delay and picked up the wee one. Puppy did not mind. It is not quite clear what happened to the rest of the litter, we see just one pup. Though it was not easy for her to carry the pup, cat is very determined. She heroically carried the pup to safety that was heavy enough. At least, much heavier than kittens.