Jonathan Creek S01 E04 No Trace of Tracy

"Sometimes it's useful to look beyond the obvious"

Roy Pilgrim an old rocker from the 60's comes home from his run only to be knocked out and chained to his radiator. Meanwhile at four O'clock a fan of his arrives at his house and walks in. However at four O'clock all Roy saw was a frog enter and then leave...where did Tracy go...?