You are referring to Evangeline's search in Part 2. Just before the part that you are asking about, Evangeline has been moving south in search of Gabriel. She has had no luck yet, but knows that she is on the right trail. She seems to just miss him from place to place. When she finally arrives in Louisiana, she finds Basil. Basil incorrectly assumes that Evangeline must have come across Gabriel already.
. . .and Basil, somewhat embarrassed,
Broke the silence and said, "If you came by the Atchafalaya,
How have you nowhere encountered my Gabriel's boat on the bayous?"
Evangeline is devastated once again that she has just missed him. But the news that Basil next gives lightens her spirit. He says that Gabriel cannot be far ahead because he left earlier that day. Basil says that he sent Gabriel to another area to trade mules, because Gabriel had become so moody that nobody could bear to be around him. He also tells Evangeline which route Gabriel will take. Then he tells her the best news of all: he will help her follow Gabriel starting tomorrow morning.
"Be of good cheer, my child; it is only to-day he departed.
Foolish boy! he has left me alone with my herds and my horses.
Moody and restless grown, and tried and troubled, his spirit
Could no longer endure the calm of this quiet existence.
Thinking ever of thee, uncertain and sorrowful ever,
Ever silent, or speaking only of thee and his troubles,
He at length had become so tedious to men and to maidens,
Tedious even to me, that at length I bethought me, and sent him
Unto the town of Adayes to trade for mules with the Spaniards.
Thence he will follow the Indian trails to the Ozark Mountains,
Hunting for furs in the forests, on rivers trapping the beaver.
Therefore be of good cheer; we will follow the fugitive lover;
He is not far on his way, and the Fates and the streams are against him.
Up and away to-morrow, and through the red dew of the morning
We will follow him fast and bring him back to his prison."