Sheriff Lightfoot, repulsed and dismayed
(telling) by the evidence
(passive phrase), digs into
(weak verb and preposition combination) Marsh Island’s secrets to solve the crime.
Remember, you want to write a line the agent, editor, and publishing house will use again and again with promotion. After you write your last line, you need to feel amazed and confident about it. If you doubt it, redo it.
I'll help. Donald, please forgive me if you read this...

Use one of these words in your last line: love, heart, dream, journey, fortune, or destiny.
You can choose a synonym, but place the word near the sentence's start or end.
Wolfe