He is morally responsible.

Any man who would sit there and nod monotonously like a mandarin, knowing all the while what he was doing to wreck the company, and let a friend put into a rotten concern all the cash he could scrape together, is a swindler!" "I think so too," she said, studying the rose arabesques in the rug.
There was a little click of her teeth when she ended her inspection and looked across at Mortimer.

Something in her expressionless gaze seemed to reassure him, and give him a confidence he may have lacked.
"I want him to understand that I won't swallow that sort of contemptible treatment," asserted Mortimer, lighting a thick, dark cigar.
"I hope you'll make him understand," she said, seating herself and resting her clasped, brilliantly ringed hands in her lap.
"Oh, I will--never fear! He has abused my confidence abominably; he has practically swindled me, Lydia.

Don't you think so ?" She nodded.
"I'll tell him so, too," blustered Mortimer, shaking himself into an upright posture, and laying a pudgy, clinched fist on the table.

"I'm not afraid of him! He'll find that out, too.