Tess Gerritsen draws on her experiences on an African safari in Die Again, her 11th novel featuring Det. Jane Rizzoli of the Boston PD and medical examiner Maura Isles.

Don’t get out of the jeep.” That’s the first thing my husband and I were told when we arrived at our safari lodge in Sabi Sands, South Africa. As long as you stay in the vehicle, wild animals consider you part of one enormous beast and they won’t attack. But the instant you step out of the jeep, you’re prey. To emphasize that point, our bush guide Greg told us about a pair of tourists who didn’t heed the warning and jumped out of the vehicle to take photos of lions. They were instantly attacked and killed. “It’s my job to keep you safe,” Greg said. “So always do what I say.”

A few days later, that advice saved my husband’s life. Every evening in the bush, Greg would find a safe spot for us to enjoy cocktails and watch the sunset. That afternoon we parked on a hilltop, with glorious views all around. There were six tourists in our truck, and as we climbed out to stretch our legs, my husband, Jacob, said he needed to answer the call of nature. “I’ll just go over there,” he told Greg, pointing to a clump of bushes.

“No, a leopard was seen down in that valley earlier today,” Greg said, and pointed him in the opposite direction. “Why don’t you go there instead?”

Thirty seconds later, a leopard strolled out of the very same bushes where my husband had originally been headed. The leopard walked toward us. At that terrifying moment we were all out of the jeep, desperately clutching our cocktails.

Greg yelled: “Everyone freeze!” Calmly, deliberately, he moved between the leopard and us, his shoulders squared, arms spread wide. He was using his body as a human shield to protect us. For a few tense seconds he and the leopard regarded each other. Then she decided that this particular prey was not worth her trouble, and she wandered back into the bushes.

Back at the lodge that evening, as the six of us nursed cocktails with shaky hands, we all agreed that no place in the bush was truly safe. I thought of how confidently Greg had faced down that leopard. I thought about how completely we trusted him to keep us safe.

Then I had a chilling thought: what if he wasn’t the man he claimed to be? What if the bush guide who met us at the remote airstrip was really an impostor, who’d come to collect a truckload of new victims? That’s how a thriller writer’s mind works. We see frightening possibilities behind every incident. We think: “what if?” and the answer always leads us to dark places.

In Die Again, that dark place is the Okavango Delta in Botswana, where seven tourists have flown in for the safari of a lifetime. Surrounded by countless perils, they rely on their hired guide to keep them safe. But days into the journey, their truck suddenly won’t start, and they’re stranded deep in the wilderness.

Six years later in Boston, while investigating a series of bizarre murders, Det. Jane Rizzoli learns that her case is linked to that same doomed safari in Botswana. Now Jane must track down the one person who has seen the killer’s face: the safari’s sole survivor.

A survivor who doesn’t want to be found.