Calling a Dead Man by Gillian Cross
When John, an explosives expert, dies in an accident in Russia, his sister Hayley and his friend Annie go there to mourn. Before long they begin to suspect that there is more to John's death than meets the eye, and that certain people are desperately trying to keep them away from the truth. They say that John had been drinking and made a mistake with the explosives. But Annie doesn't believe that, and she is determined to find out what really happened. Their search for the truth takes them deep into the country, following the signal of John's satellite phone. What they eventually find raises as many questions as it answers, and there are no easy solutions for any them.