Tobey Maguire is back as the world’s most famous arachnid superhero, and director Sam Raimi spins intricate character exploration, breathless action and threads of levity into an introspective, thrilling continuance of the Marvel comic-book series as summer-movie blockbuster. Maguire brings an otherworldly gaze to the party as he seamlessly oscillates between the identities of the brilliant, nerdy, love-challenged student Peter Parker and the web-slinging crime fighter Spidey. The basic plot pivots on a laboratory disaster that leaves Dr. Otto Octavius (a commanding Alfred Molina) fused with artificially intelligent mechanical tentacles and a compulsion to reconstruct his experiment on a grander scale. And the several themes here talk of consumptive revenge, guilt, emotional conflict, the freedom to choose one’s own destiny and the great responsibility that comes with great power. The returning cast includes Kirsten Dunst as Mary Jane Watson, now the toast of Broadway; and James Franco as Parker’s pal Harry Osborn, now a corporate power broker.