A nightmare scenario in Upper Darby was thwarted by a good Samaritan last week.
According to authorities, the stranger stepped in to help after hearing screams near his home on Oct. 15.
Surveillance video shows the suspect, Khrishon Parker, approaching Shianna Carter as she arrived home with her 2-year-old daughter, Layla, in her arms on the 7000 block of Emerson Avenue in Upper Darby…