If you are in Salem now and want something this evening, the calendar in the booking panel below is the only live answer: it shows the slots actually running today, on today’s date, and a tour that is full simply does not appear. That is worth two minutes before you walk to a meeting point, because the listing for our pick says in its own words that space is limited and advance booking is strongly suggested.
Any evening slot from about seven onward is dark through October — sunset in Salem falls from 18:24 on 1 October to 17:37 on the 31st, and the clocks go back on 1 November. An earlier slot is not a worse tour, it is a different one: you see the houses and the carved dates, and the dark arrives during the walk.
Every tour on this page meets in the centre, within a few minutes of each other and of the commuter rail station, so a late decision costs you a short walk rather than a taxi. Walks run in most weather; brick sidewalks are uneven and wet leaves make them slick, so wear shoes you can walk a mile in. On an October weekend, book before you travel rather than tonight — that is when the after-dark slots go first.