Quotation from: The Call of the Wild

Written by: Jack London

For two days and nights Buck never left camp, never let Thornton
out of his sight. He followed him about at his work, watched him
while he ate, saw him into his blankets at night and out of them
in the morning. But after two days the call in the forest began
to sound more imperiously than ever. Buck's restlessness came back
on him, and he was haunted by recollections of the wild brother,
and of the smiling land beyond the divide and the run side by side
through the wide forest stretches. Once again he took to
wandering in the woods, but the wild brother came no more; and
though he listened through long vigils, the mournful howl was
never raised.