Why didn't Holmes, Watson or Sir Henry try to help Cecile

SPOILER

At the end when Cecile falls into the mire I always wondered why Holmes, Watson and Sir Henry just stand there without making any attempt to try to run to pull Cecile out. Perhaps Sir Henry was still in shock and dazed by the attack of the dog on him but Holmes and Watson could have immediately run to assist her. I know she did wrong and would have had to answer for her part in the conspiracy but seeing as Sir Henry had fallen in love with her I could see him trying to convince the authorities that she had been brainwashed by her father and was not responsible for her actions. The romantic feelings that Henry had had for her had to have been effected by her actions and her disclosure that she was a Baskerville although it was unclear how closely they were related, perhaps several cousins removed. But still I would think his compassion would have leaned him towards urging leniency towards her. Of course it's assumed that she died although they could have run to get her out after that scene although it didn't look like they had any intention of trying to help her or maybe she could have grabbed onto something to pull herself out. When I first saw this movie I had thought Cecille, though starting out to trick Sir Henry would find herself falling for him too and try to stop her father or warn Henry. In many stories of this nature that is often how it is written.