Quantum theory is strange because it lets entities do strange things like be in two places at once, but relativity is stranger because it lets space and time do strange things like contract and dilate, which is almost unthinkable. If an electron is a point on a screen, quantum theory changes the point but relativity changes the screen itself, as special relativity illustrates.
QR5.2.1. Our Reality Bubble
QR5.2.2. Invariance
QR5.2.3. Maintaining Causality
QR5.2.4. The Ultimate Messenger
QR5.2.5. The Universal Speed Limit