Hi, can somone please tell me how John saw the hound exactly as sherlock told him, even though he was not exposed to the poison gas.  yes there were leaking pipes, but they didnt contain the poisonus gas coz it was in the facility.  thanks :)

Does anyone understand the connection between the begining scene, where Sherlock is covered in blood holding the harpoon, to the rest of the episode? Thanks! -Erin 

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