There wasn't much outside the home in the 14900 block of James River Lane: an investigator's discarded rubber glove, and a long trail of water used to wash away a young boy's blood. Hours before, according to authorities, it had been the scene of a gruesome assault in which a woman allegedly beat and repeatedly stabbed her 4-year-old son, "gravely" injuring him and forcing a mad scramble to save the young boy's life.