Plum attended Woodbury High School, where for three years he played football (as quarterback and kicker), baseball (as a power hitting catcher), and basketball.
He led an undefeated football team that won both the Colonial Conference and South Jersey Group III titles.
[5][1] Plum got onto the field at quarterback in the fourth game of the 1957 season when starter Tommy O'Connell got hurt against the Philadelphia Eagles.
[1][2][5] O'Connell left the NFL after the 1957 season,[6] and over the next four years, Plum was a consistent part of an offense built around the running of Jim Brown and Bobby Mitchell.
[8] In 1960 and 1961, Plum's backup was Len Dawson, who went on to have a Hall of Fame career with the Kansas City Chiefs of the American Football League.
[12][13] Late in the season, head coach George Wilson benched Plum several times in favor of Earl Morrall.
[1][2][4][15] The Lions traded Morrall to the Giants before the 1965 season,[16] and Plum struggled that year, completing fewer than half of his passes.
[17] Plum backed up Roman Gabriel on the 1968 Rams and Fran Tarkenton and Gary Wood on the 1969 Giants, playing sparingly both years.