from the back of the book:
Pregnant, abandoned by her lover, and desperate, Helen boards a train heading west. She meets Patrice, a happy young expectant mother who's traveling with her husband, Hugh, to meet his family for the first time. Patrice lets Helen try on her wedding band - just before the train crashes, killing Patrice and Hugh. Thinking Helen is their widowed daughter-in-law, Hugh's family welcomes her into their rich and loving home. For the first time, Helen's life is good - until her ex-lover comes to town with blackmail on his mind.
This book has been adapted for film several times, and Senses of Cinema has this to say about the book:
The opening section of I Married a Dead Man is pure Woolrich, focusing on a “typical”, vulnerable, person trapped within a hostile universe with little hope of salvation. Although the specific nature of the “trap” varies from novel to novel, its function is always the same – to dramatise Woolrich's paranoid view of existence whereupon the individual is shown to be impotent and unable to understand, let alone control, his or her world.