Banacek, a suave, debonair, freelance insurance investigator, only takes on the impossible cases and at twice the normal recovery fee. Insurance companies are loath to call on his services for the recovery of lost or stolen insured items because of these fees. Nevertheless, they call on him when they get stuck, as no one else can solve these impossible cases.
A self-made millionaire, and living in Boston's posh Beacon Hill area, Thomas Banacek (played by actor George Peppard) has a taste for only the finest things. Being of Polish decent, he also loves to recite enigmatic Polish proverbs.
Although there always seemed to be a career insurance agent looking to beat Banacek to the prize, thus saving the insurance company Banacek's hefty fee, the most strong-willed of them was Carlie Kirkland (played by actress Christine Belford). Her plan was simple, get close to Banacek, learn what he finds out and recover the item just before Banacek can.
Banacek is aided in his efforts by his limo chauffer and gofer, Jay (played by actor Ralph Manza). Jay usually has his own ideas on how the items were taken, and also has dreams of recovering the items himself first and getting the reward.
Banacek also relies heavily on his close friend and bibliophile/bookstore owner Felix Mulholland (played by actor Murray Matheson) to help in background research.