Standoff At Midnight Mountain by Mary Alford

Her brother is missing

And she's the next target

After her CIA operative brother disappears, leaving behind only a cryptic message, armed men target former agent Rachel Simmons for information. But with help from her ex, Agent Alex Booth, Rachel eludes them, trekking into the mountains in search of her brother. Pursued through the wilderness by highly trained – and very familiar – men, can Alex and Rachel expose a conspiracy that goes deeper than they ever imagined?