Answer:
What happens to the doctor Lanyon in chapter 6 of Dr. Jekyll and Mr. Hyde is that he gets ill and dies.
Step-by-step explanation:
Lanyon, Utterson and Jekyll were great friends. They had begun to meet again and everything in their lives seemed calm.
After having been meeting for two months, the lawyer was denied entry to Dr. Jekyll's house.
Later, he decided to go to Lanyon’s house. He appeared to be mortally ill, and he was really mad at Jekyll. He said he never wanted to hear from him again. After that meeting, Lanyon dies in less than a fortnight.
The reason why Lanyon became ill was because he could not bear to see the transformation of Jekyll, so much so that he internalized his pain becoming a physical illness that led to his death.