There is provided a control apparatus comprising: a receiving unit that, from one of a first communications terminal and a second communications terminal, each of the communications terminals being capable of sending and receiving images and messages and of displaying messages and images, receives a notification indicating detection of an outside party who is not a communicant with either of the communications terminals; and a control unit that, when the receiving unit does not receive the notification from the first communications terminal, causes the first communications terminal to display a captured image sent by the second communications terminal, and when the receiving unit receives the notification from the first communications terminal, causes the first communications terminal to display a substitute image for display in place of the captured image.