More often, his mental apathy was broken by bursts of vicious temper and violent ill humor. This I could only excuse on the basis of his illness.

13 seconds sound clip from the The Fall of the House of Usher (Escape) classic radio play.

You can hear this line at 00:09:39 in the radio play.

Quote context

[...]

- Oh, what tragedy. The sympathies of my heart go out to you.

- Oh, but leave it for the present. Leave it to dream of all those happy days we left so far behind.

- Everything will be different now that you're here. Do you remember when we were...?

- But the happy forgetfulness which Roderick found in my coming was short-lived.

- And, in a few days, he had sunk into a morose torpor from which only occasionally, with frantic difficulty, could he reach the joy of our first few hours of meeting.

- More often, his mental apathy was broken by bursts of vicious temper and violent ill humor. This I could only excuse on the basis of his illness.

- And that illness began, in my mind, to assume a most mysterious character.

- I was being unable to divine its true nature from Roderick's hesitant offerings...

- I took the liberty of questioning the physician a few days later when I chanced to encounter him in a hallway.

- Yes, she's resting as well as might be expected.

[...]