“The Love Parade” is like a Japanese fan that slowly opens, revealing a beautifully painted landscape while still concealing the face behind it. What we learn about Miguel del Solar is divulged by the huge cast of characters he interviews for his book, each of whom embodies a fragment of his past. He is investigating a murder (or murders) that took place at the Minerva building where he lived as a child, a European-style mini-castle built in 1908 to house the representatives of foreign governments in Mexico City.