Peyton Flanders seemed to be the perfect nanny, but secretly she was out to wreck the lives of the family she was supposed to be helping. Before becoming the nanny, Peyton had a miscarriage, and blamed it on Claire (the mother). Claire suspects nothing, having never met Peyton before.

In the Dzhugdzhur Mountains, Eastern Siberia, the criminal Dieter Von Cunth robs a Russian X5 nuclear warhead. Colonel James Faith travels to Rio Bamba, Ecuador, with the efficient Lieutenant Dixon Piper to summon the retired special operative MacGruber to retrieve the X5. MacGruber is considered deceased after the death of his beloved wife Casey by his archenemy Cunth in their wedding. MacGruber teams up with Piper and Vicki St. Elmo and they learn that the evil Cunth intends to use the warhead...