Based on the information present in the given passage, you need to write a correct answer to the given question. A correct answer is one that correctly and completely answers the question. Do not write answers that address the question partially or incorrectly. The correct answer must be contained in the given paragraph.
Example: Paragraph- Sent 1: Obama was born on August 4, 1961, at Kapiʻolani Maternity & Gynecological Hospital in Honolulu, Hawaii.
Sent 2: He is the only President to have been born in Hawaii.
Sent 3: He was born to a white mother and a black father.
Sent 4: His mother, Ann Dunham (1942-1995), was born in Wichita, Kansas, of mostly English descent, with some German, Irish, Scottish, Swiss, and Welsh ancestry. Question: How old was Obama's mother when he was born?
Example solution: 19.
Example explanation: Obama was born in 1961. His mother was born in 1942 and 1961-1942=19. Therefore, any of the following responses are considred correct: '19' and 'almost twenty'.

Problem: Paragraph- Sent 1:  The one person who, by his interference, could have settled all doubts was debarred by circumstances from interfering in the matter.
Sent 2: Wykham Delandre had quarrelled with his sister--or perhaps it was that she had quarrelled with him--and they were on terms not merely of armed neutrality but of bitter hatred.
Sent 3: The quarrel had been antecedent to Margaret going to Brent's Rock.
Sent 4: She and Wykham had almost come to blows.
Sent 5: There had certainly been threats on one side and on the other; and in the end Wykham, overcome with passion, had ordered his sister to leave his house.
Sent 6: She had risen straightway, and, without waiting to pack up even her own personal belongings, had walked out of the house.
Sent 7: On the threshold she had paused for a moment to hurl a bitter threat at Wykham that he would rue in shame and despair to the last hour of his life his act of that day.
Sent 8: Some weeks had since passed; and it was understood in the neighbourhood that Margaret had gone to London, when she suddenly appeared driving out with Geoffrey Brent, and the entire neighbourhood knew before nightfall that she had taken up her abode at the Rock.
Sent 9: It was no subject of surprise that Brent had come back unexpectedly, for such was his usual custom.
Sent 10: Even his own servants never knew when to expect him, for there was a private door, of which he alone had the key, by which he sometimes entered without anyone in the house being aware of his coming.
Sent 11: This was his usual method of appearing after a long absence. 
Question: What is Brent's usual method of coming home after a long absence?.

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Solution: Unexpectedly through a private door.