This story has a lot of potential. From a constructive perspective I found the large number of spelling and grammar mistakes to be distracting. Also, in some scenes the writer mixed up the characters - For example at crucial times in the story Leah was referred to as Fiona and later in the story Frank and Jack were confused at another crucial time of the story. In the final chapters the story had Jack jumping into the passenger seat of his vehicle, then the writer described Jack racing his vehicle with lights flashing etc., but Brian was actually the one driving. The good news is all these things can be easily corrected with a thorough proof read and edit, so in essence, these are only very minor criticisms and issues.
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For the most I enjoyed your descriptive narration style, but there were also some occasions where the sentences were too long, which again can be distracting to read, but easily fixed.
I thought the plot was good, but if I was to provide a comment, I would suggest that it may have wrapped up a little too suddenly with the discovery of the smoking gun evidence.
Also, as a reader, I would have liked closure by seeing the killer being held to account by receiving his/her just desserts, especially when he/she was very smug and remorseless when confronted by Jack in hospital. (Little spoiler alert) Or maybe as an alternative to receiving a suitable sentence, 'something' could. happen to the killer whilst recovering in hospital to make it final, rather than implied - i.e.Jack sneaking back in to exact his revenge, or an obliging nurse/doctor etc who did the world a huge favour etc. But overall I enjoyed the story which I believe has a lot of potential. Good Luck with your story.