Learn Russian: Вдруг в доме погас свет. - Suddenly the light in the house went out.

In Russian, when an event happens suddenly and introduces a new subject to the scene, the verb often precedes the subject. Because the setting (в доме) and time (вдруг) are already established at the start of the sentence, placing погас before свет keeps the focus on the sudden action itself.

What is the infinitive of погас, and why doesn't it have a standard past tense ending?

The infinitive is погаснуть (to go out, to extinguish - perfective). Many perfective verbs that end in -нуть drop the -ну- suffix in the past tense. This gives us the masculine form погас (rather than погаснул). The feminine form would be погасла, and the plural is погасли.

How does this sentence relate to the не успел ... как construction from this lesson?

This sentence is a perfect example of the sudden, interrupting event that goes in the second half of that construction. You could easily connect it to an initial action: Не успел я открыть дверь, как вдруг в доме погас свет (No sooner had I opened the door than suddenly the light in the house went out). The word вдруг is frequently added right after как to emphasize the surprise.

Why use the prepositional в доме instead of just дома?