Quote 13
And the lawyer, scared by the thought, brooded awhile on his own past, groping in all the corners of memory, least by chance some Jack-in-the-Box of an old iniquity should leap to light there. (2.50)
His friend’s hypothetical situation prompts Mr. Utterson to examine whether he might have traveled down a similar path.
Quote 14
To this rule, Dr. Jekyll was no exception; and as he now sat on the opposite side of the fire—a large, well-made, smooth-faced man of fifty, with something of a slyish cast perhaps, but every mark of capacity and kindness—you could see by his looks that he cherished for Mr. Utterson a sincere and warm affection. (3.1)
Dr. Jekyll has warm feelings of friendship for Mr. Utterson.
Quote 15
A purse and gold watch were found upon the victim: but no cards or papers, except a sealed and stamped envelope, which he had been probably carrying to the post, and which bore the name and address of Mr. Utterson.
This was brought to the lawyer the next morning, before he was out of bed; and he had no sooner seen it and been told the circumstances, than he shot out a solemn lip. (4.2)
Mr. Utterson’s friendships help him obtain crucial information regarding the mysterious Jekyll/Hyde connection. This is how friendship drives the plot forward.