Castle's Season 7 finale is digging up old memories for Richard Castle.

Monday's season-ender (10/9c, ABC) finds Castle (NathanFillion) and Beckett (Stana Katic) investigating a murder in the woods. However, the case has eerie similarities to a traumatic event from Castle's past.

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In the first look at the finale above, Rick recalls wandering into Hollander's Woods — which gives the episode its title — as a child and seeing a figure in black presumably dumping a body. "After a few moments, he left, and that's when I saw her," Castle says. "A body, the first body I'd ever seen, Her throat had been slit and those same symbols were carved into her forehead and her cheeks."

While seeing a mutilated corpse at a young age is plenty traumatic, the last couple seconds of the sneak peek suggest that event might be seared into Castle's brain for a different reason — and perhaps made him the man he is today. "We get some answers as to why Castle became a mystery writer," creator Andrew W. Marlowe, who co-wrote the episode, previously told about the finale. "We get to go way back into Castle's backstory. It opens up some old wounds and leads to a bit of an obsession."

Check out the first look above. Castle's Season 7 finale airs Monday at 10/9c on ABC.