Hephaestus was married to Aphrodite, but she had a long-standing affair with Ares. Hephaestus hatched a plan to catch them in the act. He built an invisible golden net and set it up above his and Aphrodite's bed. He then told her he was taking a trip to Lemnos and hid. Soon, Aphrodite and Ares were in the bed together, and the net fell upon them, trapping them. Hephaestus and other Olympians came in and ridiculed the adulterers.
There are two versions of Hephaestus being banished from Mt. Olympus. One is that his mother, Hera, threw him off because he was born lame. The other, which seems to be the one told in this story, is that he was born healthy, but when he intervened in an argument between his parents, Zeus threw him off Mr. Olympus. Hephaestus fell for a full day and crash-landed on the island of Lemnos. The island's inhabitants took care of him as best they could, but Haphaestus was left crippled.