A burglary at an Indiana widow's home uncovers a shocking murder: her husband Harold 'Peanut' Allen, who died nine months earlier from apparent natural causes, was actually poisoned with ethylene glycol in a root beer float by his wife Marsha and stepdaughter Ashley. Dateline producers discuss how one burglar's loose lips cracked the case wide open. Harold Allen's tight-knit family of brothers never suspected murder despite early red flags about Marsha's cold demeanor and delayed notification of his death, showing how love and trust can blind families to danger.