When an art fraud investigator receives a package containing a stolen diamond from a man claiming to be her long-lost brother, she discovers that her father masterminded an international diamond heist and then travels to Geneva and underground catacombs in the Siberia wilderness to locate the stolen diamonds and return them to their rightful owner in order to save her father, who she thought was dead, from the consequences

i like it, but stick to the essentials: ?"a fraud investigator must track down stolen diamonds in siberia in order to save her father's life"

A fraud investigator must go to Europe and through Siberian catacombs to find out the truth about her father who mastermind an international criminal heist.

69 words - really? This is more like a short story than a logline, and it's way too complicated. You have to read it several times to understand what is going on and even then I'm still not sure.

Try and get it down to 35 words MAX and just keep the essentials:

Who is main character (protagonist, hero etc)

What do they want (what must they actively pursue and fight for to achieve their goal? What are the stakes?)

What is stopping them from getting it (What are the obstacles/oppositions in their way?)