He took more care than ever, since he was watching another, that the positions were not reversed.

More than ever he kept his eyes and ears open and his mouth shut.

Seeing Lady Arabella gliding up the stairs towards his master's room, he took it for granted that she was there for no good, and doubled his watching intentness and caution.
Oolanga was disappointed, but he dared not exhibit any feeling lest it should betray that he was hiding.

Therefore he slunk downstairs again noiselessly, and waited for a more favourable opportunity of furthering his plans.

It must be borne in mind that he thought that the heavy trunk was full of valuables, and that he believed that Lady Arabella had come to try to steal it.