Winter did not mention Tasso.

This is figurative.
An arrangement was quickly made.

He was to start that evening and meet Capella on arrival at Naples; Winter would telegraph the fact of the Italian's departure according to programme.

Holden was not to spare expense in employing local assistance if necessary.

He was to report everything he could learn about Capella's movements.
Brett wanted to hand him L50, but found that all the money he had in his possession at the moment only totalled up to L35.
Winter produced a small bag.
"It was quite true what I said," he smirked.