This was the biggest charting success of Crispian St. Peters, and one of only two Top-40 hits in his career - the other one was "You Were On My Mind," which made #36 in the US and #2 on the UK charts in 1967. He was born Robin Peter Smith.
St. Peters worked in the UK for various small local bands, including The Hard Travelers, The Country Gentlemen, Beat Formula Three, and Peter & The Wolves. An EMI publicist picked him up for the Decca Records label, and the rest if a very modest part of history.

According to biographies we've dug up, St. Peters spent more time boasting to the press than he did recording, sweepingly declaring himself of even mettle with the Beatles, Elvis Presley, and Tom Jones. He also had psychological problems and ill health, succumbing to stroke in 1995. His charting career was over with by the time of Woodstock, but he did make a stab at a comeback in the '80s.
The title of course refers to an old fairy tale: The Pied Piper of Hamelin. It originates in Middle Ages Germany. A town hires a rat-catcher to rid their city of a rat infestation. Said ratter arrives in a costume that looks somewhat like a court jester and does his thing with a magic flute, which leads all the rats away. The town then refuses to pay him, so in anger he pulls his flute trick again, this time leading away the children. The Pied Piper, like many fairy tales, is embedded in modern culture in music, literature, and film the world over.
"The Pied Piper" also got covered a couple of times by Del Shannon and the Jamaican reggae duo Bob and Marcia.