This plant goes by the name Datura, Thorn Apple and others. It planted itself in a pot meant for marigolds. I feel very lucky.
It's a very poisonous plant. Below is a description from Wikipedia. All parts of Datura plants contain dangerous levels of the tropane alkaloidsatropine, hyoscyamine and scopolamine which are classified as deliriants, oranticholinergics. There is a high risk of fatal overdose amongst uninformed users, and many hospitalizations occur amongst recreational users who ingest the plant for its psychoactive effects. Datura intoxication typically produces delirium (as contrasted to hallucination); hyperthermia; tachycardia; bizarre behavior; and severe mydriasis with resultant painful photophobia that can last several days. Pronounced amnesia is another commonly reported effect. The onset of symptoms generally occurs approximately 30 minutes to an hour after smoking the herb. These symptoms generally last from 24 to 48 hours, but have been reported in some cases to last as long as 2 weeks.
This must be the "Thorn Apple".
It's a beautiful but deadly plant. I think it could be named "The Angel of Death" !