Sometimes you just can't shake the idea that an author really doesn't like their characters much. Flaws and troubles aplenty are one thing - but weighing everybody down in a story with just about every possible problem known is another kettle of fish altogether.
We know from the blurb that Detective Parker Bell has just returned to work after shooting dead a killer - which turns out to be somewhat less straightforward than it seems. As does the abduction case he and his partner are handed on his return. A young woman being held, a list of clues pointing to others who will also die, with the added knowledge that the abduction victim supposedly will be released if they allow the other nine to die. Needless to say the clues are sort of obscure until women actually do start dying, and a connection can be found.
Along the way a potential victim is identified, and whilst she serves as the unrequited love interest for Bell, she's also one of the people who could help identify the killer, but she, and the other nominated victims / friends, steadfastly refuse to do so. Because we're now into spoiler territory this is going to get difficult, but suffice to say there are a group of women with a shared secret, and a killer that they are protecting for reasons that needed a very big glass of water to swallow. There just didn't seem to be any good reason for the whole scenario that was developing before the readers eyes. Although, to be fair, you can get mightly distracted from that by the whole crush / romance thing going on between the lead investigator and the "lead potential victim" which was just ... well uncomfortable and pretty well unbelievable.
That's not to say this isn't well-written or isn't likely to have some appeal to some readers, but for any that are plot and motivation driven, it could be that whilst the idea behind A SECRET TO THE GRAVE is an intriguing one, the character motivations are unconvincing and the amount of baggage everyone was carrying unfathomable.