Call the Midwife2012

[Sister Monica Joan has been found by the police, wandering on the banks of the River Thames, dressed only in her nightdress]

Sister Bernadette:
We don't know whether she has dementia or whether she's just wilfully eccentric.

Dr. Turner:
I understand. There are more medical treatises written about senile decay than you can shake a stick at. But I keep to one invariable diagnostic rule: if they're brought back by a policeman in their nightie, then they've got it.