Mary Morris; Mink Morris (daughter of Mary Morris); Henry Morris (Mary's husband); Joseph Conners; Anna; Peggy Ann; Helen (Mary's friend in New York); Tim (Helen's son); Drill (villain, a Martian)
Mrs. Morris, at first, thinks nothing of her daughter and a friend playing their game of "invasion". But when Mink starts telling of a Martian named Drill, who is the fore-runner of a Martian invasion of Earth, and Mary discovers that kids of her friends in other parts of the country are playing the same game, she wonders if this is for real.
Colonel Lawrence Ardsley (death); General Minorly (Medical doctor); Colonel David Todd (villain); Lynn Ardsley (villain, Lawrence's wife)
David Todd and Lynn Ardsley plot her husband's murder, while David and Lawrence are on a mission to Mars to investigate the planet's landscape and possible life forms. The crime is committed, but with unexpected consequences for David!