The Lost Arrow starts off with Sarah on a boat seven miles above the Mariana Trench, reading scans from the bottom of the ocean. But there's an anomaly on a scan that is something management on the boat isn't expecting. This scan is a problem for Trin, a super-smart member of the crew of the ship the boat seven miles above has just found. But the technology of Trin's ship is way beyond Earth's, so where did he (and it) come from? Since this book starts by going back and forth from Sarah and Trin's point of view it would be a more interesting story once their storylines start to intersect more. For the start of the book it seems more like two different stories are being told. Some of it seems a little cliché, but it's interesting and plausible enough that I'd keep reading.