The group had planned to head to the studio once again in May of that year to record, "Under the Boardwalk", written by Kenny Young and Arthur Resnick. On the 21st of that month however, Lewis died of a suspected heroin overdose. Instead of canceling the studio session, they asked a former member of the group, Johnny Moore to sing the lead.
The song was intended to be an uptempo, upbeat song. No one seems to be sure if the change was made intentionally, but the shift from major to minor (which WAS part of the song), along with the slowing down of the melody changed the feel entirely. It became the last top ten hit for the group although they continued hitting the charts up until 1967. They continue to perform today and you can see more about the group now, and their legacy here: http://www.thedrifters.co.uk/