It is in Chapter Three of this great book that you will find the answer you are looking for, when the narrator of the story arrives at the house of the Time Traveller only to find that his host is not there for he has been "detained." However, suddenly, and dramatically, The Time Traveller enters the room where his guests are and it is his appearance above all that causes great uproar and indicates that he has obviously just gone through a trying experience. Note how the narrator describes him:
He was in an amazing plight! His coat was dusty and dirty and smeared with green down the sleeves. His hair was disordered and, it seemed to me, greyer--either with dust and dirt or because its colour had actually faded. His face was ghastly pale; his chin had a brown cut on it--a cut half-healed; his expression was haggard and drawn as by intense suffering. For a moment he hesitated in the doorway as if he had been dazzled by the light. Then he came into the room. He walked with just such a limp as I have seen in footsore tramps. We stared at him in silence, expecting him to speak.
Of course, the details of his limp and "haggard and drawn" expression clearly indicate that he has gone through a trying experience, but it is only as we continue the story that we find out the truth of what really happened to him during his dangerous adventure in the future.