"My immediate thought was: 'This is a terrible idea. This is obviously evidence of a crime and we have now brought it back to our condo,' " the author tells PEOPLE
Megan Miranda typically doesn't mine her daily life for book inspiration. But when she discovered a washed-up phone on the beach during a family vacation, she couldn't help but think of the thriller potential.
It happened on a trip to visit in-laws in Puerto Rico, and her husband had shattered his own phone in the door of their rental car earlier in the getaway, an already "ominous start to the trip," says Miranda. The next morning, her husband and teenaged daughter stumbled on a stranger's phone in the sand while on a walk.
"They saw something washed up in the surf and they bent down to pick it up and it was a phone," Miranda, 41, tells PEOPLE.
"Immediately I was like, what are the chances of that? You lose a phone one day and then you find one? A phone literally washes up at your feet? I feel like if I wrote just that no one would even believe it. Such a weird coincidence."
They brought the device back to their condo. The phone, "cracked, coated in sand and water," appeared dead.
"They thought, 'Let's see if we could get it to start and find out who it belonged to.' I don't know if it's because I read a lot of thrillers or because I write them, but my immediate thought was: 'This is a terrible idea. This is obviously evidence of a crime and we have now brought it back to our condo.' Their reaction was, 'Why do you think that way?' And mine was, 'Why do you not think that way?' "
It was a days-long process that followed, one that involved allowing the lost-and-found phone to sunbathe on their balcony. Soon, it held a charge and turned on just enough to locate a number to contact. Luckily (depending on how one looks at it), there was no passcode — "which was Weird Coincidence Number 3 to me," she jokes.
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"Of course again, because I write thrillers, I was like, well, now we've made another mistake in the horror-movie scenario where we've turned on this phone and now if it was part of a crime, someone could track it down to us," says Miranda.
Her family, now "excited about the prospect of trying to find the owner," texted the number they found via a different device and got in touch.
"We found out that they had lost it two weeks earlier while on vacation in Puerto Rico, and we shipped it back to them," she says. "So it had this happy ending to it, but in the back of my mind, all I could think was, 'What if this had been something nefarious? And how could the people who both lost and found a phone be connected?' It kicked off this whole completely different idea."
From that spark came The Only Survivors, Miranda's latest novel, in which the main character similarly comes across a washed-up phone early in the story about a group of unlikely friends trauma-bonded by a deadly incident from their past.
And, no, the owners of the real-life missing phone are not aware they inspired a book, as far as Miranda knows.
"We really didn't have much contact after that. They seemed very excited that we had found it and to be able to have it back because I'm sure so many of us have so much of our lives on our phone. I don't know if they ever got it working again," says Miranda. "It was one of those lives-intersecting moments, and we just went on our separate ways from there."
The North Carolina–based writer and mom of two was first a scientist with a degree from MIT before becoming a bestselling author. Her time as a high school science teacher inspired her first young adult books, then she eventually transitioned to adult mysteries.
Her novels include All the Missing Girls, The Perfect Stranger, The Girl from Widow Hills, Such a Quiet Place, The Last to Vanish and The Last House Guest, which was a Reese Witherspoon Book Club pick.
"I was a kid who loved mysteries and suspense and thrillers — and I was also a kid who was afraid of everything," Miranda says. "Why am I drawn to these stories? I think as the reader, you're taking the journey through and you're making it through the other side of it. That's how I approach the writing of it. ... Maybe thrillers are a way of working through things in these hypothetical situations, in a safer way, and learning about other people. And maybe also yourself."
Miranda says her two teens read her books (and offer their "honest" feedback), and her ability to spin everyday happenings into potential dark mystery plot lines is a running joke among her family.
"They're happy to rate my books against one another too. It's pretty funny," she says, adding, "I think it's become a little bit of a family joke at this point. My kids are like, 'Only my mother would take the story in that direction.' Here's this nice scenario of we found a phone and we're able to return it back, and suddenly I was like how can I turn this lovely family vacation and nice happy ending into this creepy, dark and twisted idea instead?"
"I've always been someone with an overactive imagination, thinking worst-case scenarios, which is helpful when you're writing a book but not existing in your daily life as much," says Miranda. "But it does create a lot of story ideas, just taking this little spark of something and pushing it to an extreme."
The Only Survivors is now available wherever books are sold.
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