When an affair leads a recluse yachtsman and cameo actress to discover one another career tramps they team up to fleece the jet set but recluses ex returns to love and revenge as an IRS sting – SuperTramps

Agreed with the above comments. Also this sounds like a great setup for a comedy more so than a thriller.

Does the story begin when they discover each other is the impostor or does the story end with the discovery?
Does the audience know that each is an impostor or is it a big reveal...
Because different scenarios will change how the logline is written.

Also, I would remove the comma. It's not necessary and slows the read.