What do honest people do if someone else's thing accidentally falls into their hands? That's right, they are trying to find its owner. That’s what Katya and Tomka did when they found an expensive camera forgotten by someone in a trolleybus. The girls were just going for a walk to the zoo, so they decided to take a photo with him and buy a new film for the owner. That's what they did. Moreover, the person to whom the device belongs soon showed up... It would seem that we can forget about this story. But the girls noticed that the owner of the loss looked at his camera as if... he was seeing it for the first time in his life! Having developed the film, Katya and her friend noticed: the photographs taken before them depicted places well known to them... But who is this suspicious face looking out of the window? There is some kind of secret here! And the girls decide to solve it...