Long short Story:

Hercules was a San Bernard that stayed by Chantilly's side, helping him and protecting him against other dogs in the shelter Chantilly was thew into before being adopted by Master (consequence that unleash in being both apart and weeks later Chantilly discovers that Hercules was killed by poison in the same shelter).

Of course he miss Hercules, the first and the most important friend, almost like a father to him, i bet he'll never forget.