Aiding and Abetting

Aiding and Abetting is Muriel Spark's mordant and witty satirical take on the true crime genre, a novel of fraudsters, imposters, murderers and aiders and abetters.
In Paris, a psychiatrist finds herself treating two elderly gentlemen who both claim to be the notorious British fugitive Lord Lucan. But who, if either, is the real Lord Lucan? Can she discover the truth before her own dark secret is revealed?