Describe the pun "If he be Mr. Hyde", he had thought, "I shall be Mr. Seek."
In chapter 2 ofThe Strange Case of Dr. Jekyll and Mr. Hydewe witness how Mr. Utterson, who is Dr. Jekyll's lawyer, begins to make slight connections of the possible relationship between the man whom Enfield speaks about (Mr. Hyde), and Utterson's client, Dr. Jekyll.
Mr. Utterson is aware of the story told by Enfield in chapter 1, about how a mysterious man, a "Mr. Hyde", ran over a child one night and then said, as nonchalantly as ever, that he would repay the family with money. This, he does using checks that belong to Dr. Jekyll.
Although the story is already known to Mr. Utterson, the information that Enfield provides gnaws into Utterson's curiosity quite deeply. This is because Mr. Utterson possesses a document in which Dr. Jekyll basically leaves his entire fortune to Mr. Hyde in the event of his death.
Dr. Jekyll is a man well-respected for his attainments in medicine. However, Mr. Utterson finds both vulgar and improper that Dr. Jekyll would have these attentions towards this strange man, Hyde.
He finds it especially odd that Dr. Jekyll includes in his documents possibilities as to his own "potential disappearance", stating how, in the event of this happening, Mr. Hyde should benefit entirely from all of Jekyll's possessions.
......Mr. Utterson, though he took charge of it now that [the will] was made, had refused to lend the least assistance in the making of it; it provided not only that, in case of the decease of Henry Jekyll, M.D., D.C.L., LL.D., F.R.S., etc., all his possessions were to pass into the hands of his “friend and benefactor, Edward Hyde,” but that in case of Dr. Jekyll’s “disappearance or unexplained absence for any period exceeding three calendar months,” the said Edward Hyde should step into the said Henry Jekyll’s shoes without further delay [..]
Any learned man who witnesses another intelligent man acting in this manner must wonder who exactly is this Mr. Hyde, and what or why would Dr. Jekyll allow him so many liberties and rights on his behalf. Moreover, why would Dr. Jekyll even have relations with a man capable of running over a child and repaying a suffering family using Jekyll's own money!
This is what originates the pun "If he be Mr. Hyde (a homophone of "hide", or "keep secret"), then I (Utterson) shall be Mr. Find". This shows that Utterson is more than willing to uncover the real secret of what is going on between Dr. Jekyll and Mr. Hyde.