What My Best Friend Did - A Gripping Psychological Thriller Novel | Perfect for Book Clubs & Mystery Lovers" (Note: Since the original title appears to be a book title rather than a product title, I've optimized it as a fiction novel with SEO keywords like "psychological thriller" and added usage scenarios for book clubs and mystery enthusiasts. If this is incorrect and you meant a different product, please provide more details.)

When Alice meets Gretchen for the first time, it feels a bit like falling in love. Life's got a bit boringly grown-up of late: weekends at weddings and baby-showers, celebrating friends' transitions to a life she isn't quite up for yet, and, at home, a sweet-and-stable boyfriend she suspects she's outgrown. Gretchen Bartholomew, with her air of impulsiveness and intuitive style, is that rarest of things: a proper, new friend who knows how to have fun. Even the added complication of Gretchen's gorgeous brother, Bailey, might actually be just what Alice needs. Before she knows what's hit her, Alice's brilliant new best friend is turning her world upside down. But Gretchen has a dark secret, which - like a time bomb ticking in her hand - won't stay hidden for ever. The explosion may teach them both more than they ever wanted to know about how female friendships can go wrong.