。
There was nobody around.
Literal
Surroundings [in-には] who [even-も] didn't-exist.
誰も + negative is one of the first universal-negation structures learners encounter: 'nobody.' The pattern is productive across other interrogatives: 何も (nothing), どこも (nowhere), いつも with negative ('never'). Adding 一人 (誰一人いなかった) intensifies it to 'not a single person.'