What was it that finally caused Joey to leave Topthorn's side. Describe the results of his panic.

Spring is a slightly happier time, and Joey and Topthorn are put into the care of an officer named Friedrich, who takes good care of them. In the Autumn, Topthorn dies. Joey refuses to leave his side, even as shelling begins. The shelling is hell for horses. Finally Friedrich dies in the shelling, leaving Joey alone.