The speaker's anger is only heightened by his fears, and his continued deception about his true feelings.
Then, in an odd, metaphorical twist, the speaker's anger blossoms into an apple. Yum! At least the speaker's enemy thinks so. One night, he sneaks into the speaker's garden (presumably for a delicious apple snack), but it doesn't work out so well for him. The next morning, the speaker is happy to see that his foe lying dead under the tree that bore the (apparently poison) apple. Not good.