I borrowed a library book once in the late 80s or early 90s which i think was a mixture of short stories from different sci fi authors. the story i am particularly interested in is about a machine that can plant evidence to frame someone (like hairs and dna and fingerprints) and disguise itself as everyday appliances if someone interrupts it (like a radio or a tv). I am pretty sure it was a short story. I can't remember much about the plot, except that the story started (I think) with the machine crawling up a wall to get into some guy's apartment and then starts planting the evidence. The idea behind the story fascinates me and I wish I could find it so I could read it again. Another short story I once read that stayed with me in the same vague way, was about a guy who is in his apartment one day when a portal opens and he gets encouraged by himself (who has just come through a portal) to go through the portal. Then, before he goes through, another of himself, but more harassed looking, comes through a portal and tells him not to go. I think the story then takes us on the trip through the portal, as he decides to go rather than listen to himself (the second himself, in fact, his other selves may have had an argument about whether he should go!) once again, very vague memories but strongly retained so that I would like to find these stories and read them again.