S4·E15 The Quincunx

A successful folk trio comprising two brothers and a sister tour San Francisco, and Eve's suspicions are roused when the girl, an old school friend, disappears without a word. When the body of another young woman turns up, brutally murdered, the Chief knows that there is a connection somewhere; but which, if either, of the brothers killed the girl? The clue to their sister's whereabouts might just be in their music.