In the frontier village Vetrov boys from the childrens home called Indians lead a bitter war with the local Símáks. Before a battle the Indians have a meeting in the sandpit with a smoke signaling. The smoke brings to the sandpit a frontier guard Tomás with a police dog Ranek. The children learn from Tomás that Rank served out and that it shall be destroyed. The nine-year old Fanda writes a letter to the minister of the frontier guards in which he asks to let Ranek live. To save Raneks life he also visits the local frontier guard commander. In the end it is decided that children from the childrens home may keep Ranek.