An accomplished American actor, he gained fame with his role as Danny "Danno" Williams on the TV series "Hawaii Five-O." Born in Los Angeles, he was the adopted son of playwright Charles MacArthur and actress Helen Hayes. His early career included notable stage performances and a debut in the film "The Young Stranger." Throughout his career, he appeared in numerous films and television shows, earning a reputation for his versatile acting skills. He passed away in 2010.