The Indian kept in the background, saying never a word, as if he belonged to another species.

印第安人躲在幕后，一言不发，仿佛他属于另一个物种。

Why he himself kept in the background, however, I could not conceive, and only sinister reasons would suggest themselves in explanation.

然而，我想不通为什么他自己躲在幕后，只有险恶的原因才能解释清楚。

He had kept in the background, sitting on his rock, but there was no need to stay behind any longer; he gets down and goes to the steamer.

他一直在后台， 坐在他的石头上， 但没有必要再留在后面了； 他下车去汽船。