Who is Clem Cottle from The Cat Who Went Underground and what is their importance?

Qwill initially hires Clem Cottle to build the addition on his cabin. Clem is engaged to Maryellen Wimsey, and the couple plans to wed in October. He is described as honest, skilled and industrious. When Clem mysteriously disappears the day before the Fourth of July parade, Qwill learns that Clem is Joanna's fourth victim.