Calculated Risk is a 1960 science fiction novel – specifically, a time travel story – by Charles Eric Maine.

In a recent nuclear war, London was left largely in radioactive ruins, survivors living huddled in miserable huts.

Desperate to escape, and born of a harsh and ruthless time, Calland does not pause to consider the moral implications of his plan involving the destruction of the original personalities inhabiting two 20th-century brains and bodies – in effect, a double murder.

Calland's equipment works as intended, he and Kay are sent back to the 20th century, and into bodies of the correct gender.

Thereupon, Calland seeks to remedy things by an even more ruthless plan – to rebuild his mind-transferring machine and use it to transfer Kay's mind into the body of his 20th-century fiancée, caring nothing about killing her in the process.