John Winchester co-owned a garage in Lawrence, Kansas with Mike Guenther until his departure following Mary's death. John, Dean and Sam lived temporarily with Mike and his wife, Kate, following the destruction of their home (See John's journal).
Sam and Dean pose as police officers investigating the unclosed case of John's "disappearance" in order to speak to Mike. He tells them what John was like before the fire, how he was a stubborn man and hated to lose, but that he also loved his family very much, and doted on Sam and Dean. He tells them how John didn't talk about happened that night at first, until he began to believe something caused the fire and killed Mary, Mike begged John to get help. He tells Sam and Dean Jonn's obsession just got worse until he was reading books on the occult and visiting a palm reader in town.