According to Alban Butler, Plechelm was an English Saxon born in southern Scotland.

[3] After being ordained, he made a pilgrimage to Rome, with two fellow monks, Saints Wiro and Otger.

Having been consecrated a bishop, perhaps by Pope Sergius I, he returned home with a number of holy relics.

They were well received by Pepin of Herstal, who gave the missionaries St. Peter's Mount (also known as Sint Odiliënberg).

With the invasion of the Normans in the middle of the ninth century, the relics of Wiro, Plechelm, and Otger were moved to Utrecht.