1920's London. A brutal, bloodthirsty murder has stained the plush carpets of an elegant London townhouse. The victim is the rich and glamorous Emily French; and all the evidence points to Leonard Vole, a handsome young man who stands to profit from the vast fortune the victim has left in her will. But he is not alone. Leonard is adamant that his partner, an enigmatic chorus girl, can prove his innocence, and his down-at-heels solicitor is swiftly convinced of this. Soon there is more than one life on the line, and a terrible fate for the guilty party lies in the hands of 'The Witness for the Prosecution'.