This is a walkthrough for my New Year's Eve Logic Puzzle over on Sporcle.
1. Charles’ clue tells us that Paris is in Paris and Sofia is in Sofia.
2. From Paris’ clue we learn that Maria is in Rio de Janeiro, and Jim is in Reykjavik.
3. Maria’s clue tells us that Janice is in Denmark, and Angela’s clue tells us that she is in the capital. So Janice is in Copenhagen.
4. Consider Jim’s clue. Ed and Mike both have to be in a European capital. The only situation where two people in different countries’ capitals can literally see each other, is with one person in Rome and the other in Vatican City. Maria’s clue tells us that Mike has to be in Rome (because of the four-letter rule), which means that Ed is in Vatican City.
5. The only square in Vatican City that shares its name with somebody in the quiz is St. Peter’s Square. So Peter is the person in Spain, and Angela tells us he is in the capital, so Peter is in Madrid.
6. Peter’s clue tells us that Joyce is in New York.
7. From Joyce’s clue we learn that somebody in the quiz is in Sydney. With Maria being in Rio de Janeiro and Joyce in New York, this means that Sydney is the third and last non-capital in the quiz. From Angela’s clue, we learn that the person in Sydney is Kristin.
8. To solve Kristin’s clue, we need to consider Janice’s clue. She tells us that somebody has to be in New Zealand’s capital, i.e. Wellington. David has to be in a European capital. The only European capital that comes after Wellington alphabetically (Kristin’s clue) is Zagreb.
9. David's clue tells us that Timothy is in London.
10. Jonah is in a city that starts with an H (Timothy’s clue). He has to be in a European capital. The only European capital starting with an H is Helsinki.
11. We know that somebody has to be in Wellington. Jonah’s clue tells us that either Spike or Natalie has to be there. As a man, Spike can only be in a European capital, so Natalie is in Wellington.
12. Jane has to be in a South American (Natalie’s clue) capital. The only South American capital with four letters (Maria’s clue) is Lima.
13. Spike has to be in a European capital. That capital, we learn from Jane’s clue, has to be between Quito and Rome alphabetically. Reykjavik and Riga fit the bill, but because Reykjavik has been used already, Spike has to be in Riga.
14. The only capitals that fit Spike’s clue are Kingston and Kingstown (Baku and Kabul don’t because of the scrambling). Because of the wording of Spike's clue (as well as the alphabetical order - Jane’s clue) Linda has to be in Kingston and Sonia in Kingstown.
15. From Janice’s clue, we know that people need to be in Jerusalem and Tokyo. Stephen, Brent and Robert need to be in Europe, so Katie and Molly are in Jerusalem and Tokyo (in any order). Because the third column has to be in alphabetical order (Jane’s clue), Katie can’t be in Jerusalem. So Katie is in Tokyo and Molly in Jerusalem.
16. Molly’s clue tells us that Robert is in Berlin.
17. If Brent is in Lisbon or Ljubljana, then Stephen is in Tallinn (Natalie’s clue). That means that Stephen can’t be in Tallinn, because Charles is. Therefore, Brent can’t be in Lisbon nor Ljubljana. He has to be in a European capital with an L (Peter’s clue). It can’t be Lisbon, Ljubljana (see before) or London (already in the quiz), so Brent has to be in Luxembourg.
18. Stephen is in a European capital where the 'Philharmoniker' orchestra performs a famous New Year’s concert. That has to be the New Year’s concert (broadcast in over 90 countries) by the Wiener Philharmoniker. Thus: Stephen is in Vienna. Done!