Mistress Wilding by Rafael Sabatini

Here was Sir Rowland Blake in high fettle at knowing himself armed with a portentous weapon for the destruction of Anthony Wilding. Upon closer inspection of it, however, he came to realize - as Richard had realized earlier - that it was double-edged, and that the wielding of it must be fraught with as much danger for Richard as for their common enemy. For to betray Mr. Wilding and the plot would scarce be possible without betraying young Westmacott, and that was unthinkable, since to ruin Richard - a thing he would have done with a light heart so far as Richard was himself concerned - would be to ruin his own hopes of winning Ruth.

Therefore, during the days that followed, Sir Rowland was forced to fret in idleness what time his wound was healing; but if his arm was invalided, his eyes and ears were sound, and he remained watchful for an opportunity to apply the knowledge he had gained. Richard mentioned the subject no more, so that Blake almost came to wonder whether the boy remembered what in his cups he had betrayed.