The captain didn't know of any local prisons, but the circumstances, to say the least, were highly suspicious.
As the death of a second spouse so soon after the first would be highly suspicious, he is powerless to do anything.
In fact, many of his actions have been highly suspicious.
The area looked highly suspicious to him, like so much of Washington these days.
He found two types, the highly suspicious and the willing business partners.
He seems to be a highly suspicious character around the school.
Suddenly, the case is over, and they've become highly suspicious.
Both groups, highly suspicious of each other, thought that they had been betrayed.
It was all very quiet, with no one about, both of which were highly suspicious.
Besides, he knew it would look highly suspicious if anyone on the road outside saw him climbing through a window.