How does what Dr. Lanyon says about Dr. Jekyll increase the mystery? From the chapter: Remarkable Incident of Dr. Lanyon

Utterson
goes to visit his old friend Dr. Lanyon, who is dying. When Utterson comments on Lanyon's
illness and brings up that Dr. Jekyll is ill as well, Lanyon says: I wish to see or hear no
more of Dr. Jekyll," and mentions that he considers Dr. Jekyll as "dead" to him.
Dr. Lanyon then repeats that he doesn't want to hear any more on the "accursed
topic."

This greatly surprises Mr. Utterson because the three men were
the closest of friends when they were younger. He mentions to Lanyon that they are too old to
form such strong friendships anymore. He wonders why Lanyon doesn't want to see Jekyll before he
dies.

After Lanyon dies, he leaves a mysterious letter with Mr. Utterson,
which is only to be opened after Mr. Jekyll dies or disappears. All of this fills Utterson with
intense curiosity about what is going on.