Vince Howard

Dr. Leonard "Bones" McCoy meets a former girlfriend when the Enterprise brings supplies to a remote archaeological survey group. Still attractive to McCoy, the woman's current appearance and her colleague hide a deadly secret, ultimately revealed as a tragedy of ecology.

Dismayed to find Samantha hard at work painting the house, Aunt Clara conjures up a top painter -- Leonardo Da Vinci. Samantha asks her to send him back but Aunt Clara can't remember the reverse spell. To make Leonardo less conspicuous, Aunt Clara zaps him into one of Darrin's suits. At his office, Darrin finds himself in Renaissance attire, with palette and paint bush. J. P. Pritchfield of Mint-Brite Toothpaste, thinks Darrin plans to use the Mona Lisa smile in his ad campaign. Darrin makes his way home and learns that Leonardo has left the house. Worried that he will be picked up, Samantha and Darrin begin a search. In a museum, Leonardo sees some modern sculpture. He thinks it is raw stone and begins to chip away with mallet and chisel. Samantha arrives in time to stop his arrest and returns the piece to its modern form. Leonardo is wrathful that his Mona Lisa will be used to sell toothpaste. Samantha tells him the only way to prevent it is to provide another idea for the advertising. Later, Darrin presents a palette of toothpaste in matching flavors, with Leonardo's picture on the package. Pritchfield is sold on this major breakthrough into the children's toothpaste market. Aunt Clara finds the reverse spell but insists that Leonardo must paint her portrait before she returns him to his place in history.

Jessica (Angela Lansbury) comes to the rescue when a friend's (Loretta Swit) sculpture is used as a murder weapon. With Edward Hibbert.

To get her out of his way while he is studying, Tony tells Jeannie to go find someone who needs help. Jeannie overhears Milton and Girard saying all their friends are up the river and she offers to help them. Milton tells Jeannie to use Tony's car, drive to the bank and withdraw some money for his favorite charity. Terrified by the note Jeannie presents, the teller stuffs her bag with bills. Puzzled by the alarm, Jeannie helps the crooks escape. Tony's car is identified as the getaway car and Inspector Conway wants to take him in, but Dr. Bellows intervenes. When Jeannie tells Tony the story, her orders her to get the money and the crooks.

Keller unwittingly leaks information to his neighbor (Brenda Vaccaro), a professional killer; guest Barry Sullivan.

Uncle Bill allows Buffy & Jody to have a friend stay over for a few days while the parents are out of town. But then Uncle Bill finds out the friend is actually a dog, and pets are not allowed in the apartment building.